I’ve been promising this post for a while now, so it’s about time. From a bike fitting perspective, I’m a fan of SMP seats. As a brand they are my most common pick for comfort, performance and client problem solving. This post will tackle the why’s and wherefore’s of SMP’s, at least as I see them, and will also attempt to give you enough information to enable you to make an informed choice if you’re in the market for an SMP.
Firstly, a discussion about seat widths versus pelvis widths. Many years ago, when I didn’t know much about pelvic anatomy, I naively assumed that there had to be link between ‘sitbone’ separation width and seat width. To that end I used to sprinkle talcum powder on a flat wooden seat and then have customers carefully lower their backsides onto the seat in their undies, and then gently stand up again, leaving what amounted to a pressure map in the talcum powder. I then tried to correlate measurements I took from that talcum powder impression with seat widths. What came out of that exercise is that there is no clear correlation between sitbone separation width and the width of a comfortable seat for that person. There is a sort of / kind of /more or less correlation around 75% of the time, with the remaining 25% being at odds with my original assumption. Sometimes wildly at odds. Being curious I was motivated to find out why and the answer lies in the shape of the human pelvis as well as the multiplicity of seat shapes, lengths, widths, tumblehomes and so on.
I need to clear up a common misunderstanding. When people talk about ‘sitbones’ this is often taken as synonymous with the ischial tuberosities which it isn’t, and I’m as guilty of sloppy language like this as anyone. One of the things I like about writing about bike fitting is that it forces me to crystallise and tidy up my thinking, and the sitbone / ischial tuberosity conflation / confusion is an instance of this. Have a look at the pic below.
This is plastic copy of a human pelvis sitting on an SMP seat as viewed from the side. The large bony protusion at the rear is the ischial tuberosity. This is not what a cyclist sits on………….unless they ride a recumbent, or possibly a Harley. We sit on the bone at the base of the pelvis as you can see above. This is the ischiopubic ramus. You will see the slight downward protrusion approximately half way along the ischiopubic ramus. The area behind that is the inferior ischial ramus [which I'll call IIR] and the area in front of that is the inferior pubic ramus [which I'll call IPR]. We bear our weight on a bike on the the ischiopubic ramus and it is the relative loading of the IIR and IPR that plays a large part in comfort.
So why isn’t there a clear correlation between pelvis width and seat width?
The picture below is the same plastic pelvis sitting on an SMP seat as viewed from the rear. Looking closely at it gives us the major clue.
As you can see, the ischiopubic ramus narrows from rear to front. What that means is that maximum width of the pelvis is less important when it comes to determining seat width than which part of the ischiopubic ramus is bearing the majority of weight and what width the pelvis is at that point. And that will depend on the how far the pelvis is leaning forward. As the pelvis leans forward , weight is being borne less on the IIR and more on the IPR where the separation width of the left and right ramen (plural of ramus) is narrower. Which means in turn that if you have a wide pelvis but are flexible enough to be able to roll your pelvis forward well and extend your back well, you may be able to comfortably use a narrower seat than would be expected. Conversely, a rider with a narrower pelvis who is inflexible and sits with a more upright position may need a wider seat than would be obvious at first glance. Naturally, there are any number of permutations of morphology, function and seat choice in between those extremes.
The chief area where SMP’s differ from other seats is the width and length of the centre cut out. If you have the ability to roll your pelvis forward on most other seats, you are jamming the soft tissue of the perineum and genitalia into the seat. With SMP’s, no problem, they’ve cut that part of the seat completely out.
The problem with this is that there is still no definitive way to say “this saddle is the best choice of the SMP range for this rider”. When I recommend a particular SMP to a rider it is usually on the basis of having observed how they function on a bike as well as their size and their global function off the bike. It is an educated guess, not a ‘fact’ and as such, I occasionally get it wrong. What I propose to do is pass on some observations gained during the successful, and occasionally unsuccessful experiences my fit clients have had with SMP’s.
So why SMP?
SMP push research linking pelvic shapes and compression issues as a major design criterion of their range. Amongst seat manufacturers, they aren’t alone in these claims but genuinely seem to have taken their thinking and the seat designs resulting from it further than others.
The list of SMP seats below is not the entire SMP range, just the dozen models that I stock or am familiar with. All share certain features.
1. None of them are flat as viewed from the side. All have a dip in the middle and and degree of dip varies from model to model. Basically, the greater the dip, the more the seat is designed for the rider to potentially rotate their pelvis forward and lower their torso. The rider doesn’t have to do this, but the potential to do it is there if the rider is functional enough to do it well.
2. All are designed to be ridden at a variety of angles from level to nose down, typically between negative 2 and 5 degrees, with the Avant, Pro and Glider being exceptions. This is measured between the high point on either side of the channel at the rear to the high point on either side before the nose droops down.
Stop Press: As of 20.12.11 the UCI has mandated that no seat can be legal if it is down more than 2.5 degrees at the nose as measured from high point at the rear to high point at the front. There is a plus / minus allowance of 0.5 degrees. That means that if you own an SMP and compete in events with commissaires controlling them, you may be subjected to a ‘seat angle horizontality’ check. If your seat angle exceed minus 3 degrees you will have to change the angle to minus 3 degrees or less. The good news is that this should have little negative impact on SMP users as the most common angle that I position fitting clients is minus 3 degrees.
3. All have a full length centre cutout, though the width varies between models. The reason for the cutout is that as the rider rolls their pelvis forward and more heavily loads the IPR, there would be uncomfortable pressure on soft tissue and nerve compression without a good sized cutout. The design of SMP’s ensures that weight is borne on the IIR or IPR or a combination of both, not soft tissue.
4. All have a Concorde like drooping nose. My assumption has been that this is to avoid catching the underside of the riders knicks on the nose of the seat when dropping back onto the seat after an off the seat effort. I’ve seen this happen, in fact had it happen on other seats, but only when wearing ill fitting knicks that were too big or when the stitching in the centre of chamois was worn leaving loose material to be caught.
5. All the steel seat rail versions have a rail that is one piece, not the usual two separate seat rails. When a seat has a large chunk of the centre cut out of it, there is a reduction in the strength and rigidity of the seat shell. This is regained by having a rail design that is separate where each side of the rail plugs into the front of the seat, but one piece at the rear. An additional factor is the thermoplastic shells seem to be made from much more rigid material than most other brands. This probably indicates a high carbon content thermoplastic, though I don’t know that.
6. The one piece rail design of the steel railed versions, as well as the carbon railed versions of the seats with thermoplastic shells, means that the rails can be replaced in event of a failure. Failures aren’t common. I’ve seen a couple and it is far less expensive to replace a seat rail than a seat. All that is needed is to undo 2 groups of 4 self tapping allen screws that hold down the 2 cantle plates that secure the rails at the rear underside of the seat shell. (see pic)
The carbon shelled models have steel or carbon rails that are bonded to the upper and so this isn’t possible.(see pic)
7. All have extraordinarily long rails. Most seats have a flat section of seat rail 70 – 75mm long. Some seats have limit markers on the rails with the seat post’s seat rail clamp not meant to be positioned outside of these limits. In some high end Selle Italia models, which are otherwise well designed seats, the limit markers are only 40mm apart. Given that Campagnolo, Thomson, 3T and many FSA seat post models (and others) have seat rail clamps that measure 40mm or more from front to rear, then seats like this have zero effective fore and aft adjustment. SMP’s are the opposite in that the flat section of the seat rails of there racing oriented seats are 95 – 100mm long. Additionally, the placement of the rail is such that it comes a long way towards the nose which means that the seat can be pushed back a long way if necessary.
8. The performance oriented SMP’s below; the Composit and Forma Families, as well as the Glider, have seat shoulders (widest point of the seat before it narrows as the nose projects forward) that are further back relative to the length of the seat than most other seats. This means that the rider sits further back relative to the length of the seat by some margin when compared to popular seats like Selle Italia SLR’s and Fizik’s Arione. In turn this means that many SMPs need 10 – 15mm less seat setback to maintain a given rider butt position in space than many other seats do. In terms of custom frame design, this often means that a frame designed for a performance SMP will need a seat tube angle that is 1 to 1.5 degrees steeper and a top tube length that is 10 – 15mm shorter to enable the rider to have the same position in space over the frame as they would on a more conventional seat. Unless there is enormous certainty on the part of the intending custom frame purchaser, I think it is smarter NOT to design a frame around a seat. Instead use a zero offset seat post on a custom frame with an SMP. That way if the rider decides to change to a more conventional seat brand / model at some future date, all they need to do is to use a standard offset seat post when they change seats.
9. The shape of the Composit and Forma Families means that when the rider rotates their pelvis forward when reaching down into the drops, the rise or kick up at the rear of the seat supports part of the gluteals that would not normally be supported on a flatter profiled, more conventional seat. That prevents the rider moving back on the seat just as the rise at the front end of the dip prevents the rider moving forward much on the seat in response to differing loads. In my view, this is a good thing. When riders have to push themselves back or forward on the seat to respond to differing loads, there is ALWAYS an issue with their position or functionality, whether they know it or not. The kick up at the rear means that the rider is anchored more securely and is more stable, particularly when forcing the gear, than is the case with flatter profiled seats. Other seats that have a similar feature are the resurrected retro San Marco Concor and the Concor Lite. I think this is important because “for every reaction there is an equal and opposite reaction”. When pushing hard on the pedals on the flat, gravity is the major opposing force to keep our backsides in place. When riding a steep hill and forcing the gear, often effort must be expended by the upper body by clinging to the bars to prevent the rider pushing him or herself off the back of the seat. The raised kick at the back of SMP’s means less upper body effort is necessary during similar circumstances as the kick provides support and a ‘backstop’ of sorts.
10. None of the performance oriented SMP’s (that is all but the Avant and the Pro) work well with
- Pinarello Dogma seat posts. The combination of proprietary seat post design and SMP rail angle does not allow the SMP’s to be set at a decent angle for comfort. Yes, they can be fitted but the seat will come loose unless you like riding them with nose up a lot at the front.
- 3T Dorico seat posts. Again, a combination of SMP seat rail angle and Dorico clamp design mean that to gain the required nose down angle often (not always) results in a front seat bolt torqued to the max and a rear seat bolt that is only lightly tightened. Result, the seat comes loose far too often.
- Many Trek, Specialized and other brands use seat posts that clamp from the sides. If an SMP is positioned a long way back on the rails with a heavier rider, they are odds on to drop at the back suddenly over bumps unless the seat clamping bolts are torqued up very, very tight. For really heavy riders with SMP’s a long way back on these style of posts, sometimes ‘very, very tight’ is still not tight enough.
11. To a lesser degree than mentioned immediately above, it is a good idea to tighten any seat post used with SMP seats as much as is sensibly possible. If this isn’t done properly, then what can happen is that over a month or 6 weeks is that the seat can slide backwards incrementally over time as the rider pushes against the kick up at the rear. Any movement won’t be noticeable day to day, but sooner or later the rider will wonder why their pedaling style feels choppy, or they are getting low back tightness. When seat setback is checked, it has often moved 10mm. I’ve seen this happen a handful of times only but the message is make sure the seat rail clamp is tightly done up. And then mark the seat rail with correction pen or similar at the front of the seat rail clamp as per the pic below.
12. Many SMP’s are available with the added designation of ‘Lady’. Glider Lady, Lite 209 Lady and so on. In each case the seat is identical to the usual version in shape and padding with the only differences being cosmetic pink stitching. SMP maintain that a human pelvis is a human pelvis and that a properly designed seat should work equally well for both genders. Another gender related piece of info worth passing on is that it is commonly reported that “Women have wider sitbones than men”. SMP beg to differ. Some research of theirs that came my way suggests that while women have wider ischiopubic ramen separation width relative to stature than men do, the average separation width is identical for both genders. My experience with fitting women and SMP’s suggests that SMP are correct that a well designed seat, properly chosen and fitted will fit both genders without problems.
13. Lastly, one of my favourites. With most seats, moving the seat forward decreases measurable seat height and moving the seat backward increases measurable seat height. Typically, if you move a seat forward 3mm you have reduced seat height by 1mm and if you move a seat backward by 3mm you have increased seat height by 1mm. Not so with performance SMP’s. SMP’s have a seat rail angle relative to seat upper that is quite different to most seats. What you will find is that the rail angle is designed like that so that moving the seat forward or backward makes little or no difference to seat height. Whether it does or not will depend on the angle (relative nose down) that you run your SMP, but within the typical range of minus 2 to minus 5 degrees, not much changes with seat height when the seat is moved forward or backward. On a personal level this confirms my view that SMP’s were designed by people who actually thought about what they were doing.
In the model explanations below, I have listed 2 dimensions. The first and larger dimension is the overall width of the saddle at the seat shoulders; i.e. the widest point. The second and smaller dimension is the effective width of the seat before it drops down more acutely as viewed from the side. What I’m trying to illustrate here is that there is not a consistent relationship between the maximum width of a seat and the effective width that can be sat on with SMP or other seat manufacturers, despite much marketing effort that tries to draw such a parallel. Effective width of a seat is affected by the lateral cross section of the rear of the seat as viewed from the rear. If the seat is perfectly flat or tapers gradually down to the sides, then the maximum width and the effective width are the same or much the same. However, if a seat tapers sharply down towards the sides then the maximum and effective widths can be quite different.
Lastly, as mentioned above, most of these seats are designed to be ridden at varying degrees of nose down. A good investment is a digital level and a long carpenters’ level. The long level is to make sure that your bike is levelled between axle centres before you attempt to quantify seat level. A degree or two difference in nose down angle can have a profound effect on seat comfort with SMP’s so it is worth recording what you find works best for you with your SMP.
Some of the pics below are of well used loaner seats while others are of new seats.
I have called the 4 seats below a Family because the unpadded Composit and the padded Evolution and Stratos share a common shell. The Carbon has a carbon fibre shell that is a close relative of the Composit shell in shape, dimension and the rate that it tapers downwards from the centre channel. I term the rate that a seat tapers down from the centre to the edge tumblehome and anyone involved in shipbuilding or design will understand why. All of the Composit family (Carbon aside) are available with the option of carbon fibre rails. The carbon railed versions have much more compliance over bumps and rough roads and save 40+ grams in weight.
Composit max width: 128mm / eff. width 111mm. Typical weight: steel rail 196 gms / carbon rail 153 gms.
When I was first shown SMP’s some years ago by their local rep, the range was much more limited that it is now. Only the Composit, Evolution, Stratos and Pro were freely available. I ordered several of each except for the Composit. I like firm, lightly padded seats on a personal level but my thoughts were “Who will ride a totally unpadded seat?” Some time later, I fitted 2 gents from Melbourne who were of similar build to me but taller, heavier versions. Both arrived with Composits fitted. I asked what they thought and both gave a strong recommendation. I rode one of the gents bikes and my immediate impression of the seat was “This is MY seat…………………..but it’s bloody hard”
I ordered one and while the shape felt perfect, I was bone sore after long rides. If I rode the next day, as soon as I got on the bike I felt like I had taken up where I left off the day before with no recovery from the bone soreness. 2 and a half weeks later I was on the verge of calling a halt to the relationship when I rode a tough 100kms on hilly and rough country roads and finished the ride without having thought about my backside once. Composits and I have got on well ever since and I have done a dozen + rides of over 200 hilly kms without problem. Yes, I had a sore backside at the end but it was a minor issue and I’ve experienced much worse on some padded seats in the past.
I like thin chamois knicks which probably didn’t help my introduction to the Composit. Anyone who rides thick chamois knicks such as can be found in some Assos knicks should be fine. The Composit tapers gradually from the centre channel for a low degree of tumblehome and is a wider platform than it looks. The Composit can be positioned from 2 degrees down to a maximum of 5 degrees down at the nose. The more flexible the rider and the greater their ability to roll their pelvis forward comfortably, the lower the seat nose should be. 5 degrees down at the nose is the practical maximum so that there is still a rise forwards towards the nose from the lowest point of the dip in the centre of the seat as viewed from the side. This is necessary to keep the rider from sliding forward on the seat.
Not many women like Composits though I’ve come across a few exceptions.
Evolution max width:128mm / eff. width: 89mm Typical weight: steel rail 256 gms / carbon rail 213 gms
Though the Evolution is built on the Composit shell, it is a much different sitting experience. It has much greater rate of tumblehome and is effectively 22 mm narrower to sit on. I have seen riders too wide for the Evolution squash them into submission over time with their weight flattening out the padding, but this is not something I recommend. In feel, the Evolution is not a Composit with padding. It is effectively narrower and does not have as pronounced a dip in the profile as viewed from the side. I sell and recommend very few of these as they seem best suited to small stature, lightweight men or women with narrow ischiopubic ramen separation width. Others can and do ride them but would probably be better off with another SMP option as a first choice.
Typically, these seats don’t work well if the nose is tilted down more than 3 degrees. Yes, there are exceptions, but in percentage terms, not many. The less pronounced dip in side on profile means that they are less suited to the rider who can roll their pelvis forward well. No problem from a comfort point of view because the large centre channel negates any chance of pressure on sensitive areas but the less pronounced dip doesn’t provide as much support under load for the rear of the pelvis as does say a Composit, Dynamic or Lite 209. Good seat but a narrow focus in terms of ideal rider shape / size / weight.
Stratos max width: 128mm / eff. width: 93mm Typical weight: steel rail 269 gms / carbon rail 226 gms
Think of the Stratos as an Evolution with more padding because that is about the size of it. The only real differences are that brand new they have an even less pronounced dip on the profile as viewed from the side and are marginally wider in effective width. Again, I don’t find many people in percentage terms that these are my first choice for.
Carbon max width:128mm / eff. width 114mm
The Carbon is basically a steel railed / carbon shell version of the Composit. I own one of each and there is very little difference when sitting on them. The Carbon can be quite harsh over rough roads because the shell has zero give. What would be ideal is a carbon railed version of the Carbon and there is, the Full Carbon which is available only in naked carbon, not colours. It is also slippery but on a personal level, I’ve never found this to be a problem because I am functional enough and have a good enough bike position to not need to slide around on the seat. I know other Carbon users who are fine with them but from time to time I come across a dysfunctional owner with poor on bike (and usually off bike) pelvic stability that complains about the slipperiness.
The other differences are that the effective width of the Carbon is a few mm wider than the Composit and the rate of tumblehome slightly less. The shape across the rear is less complex and lacks the little dips that the Composit has. I have never found this to be an issue when moving between bikes, one with a Composit and one with a Carbon. To sum up; much more comfortable that it looks but not a seat for poor road surfaces.
The Forma, Dynamic and Lite 209 all have the same shells. The Forma has zero padding, the Dynamic a thin layer of firm padding and the Lite 209 a thick layer of firm padding. These differences in padding affect the shape. The Forma family illustrates why measuring seat widths will only take one part way down the road of determining the relationship of pelvis width to seat width. All of the Forma Family are wider maximum width than the Composit Family but have narrower effective seat widths than the Composit and Carbon because of the much steeper rate of tumblehome. But they don’t feel narrower to sit on. They feel much the same, at least to this 182cm / 75kg bike rider. In isolation, I would have thought that the steeper tumblehome placed an uncomfortable shear force on the IIR but in practice, it doesn’t. The SMP’s that seem to suit the widest range of rider heights, weights and pelvis widths are the Dynamic and the Lite 209.
Forma max width:135mm / eff. width 92mm Typical weight: steel rail 220 gms / carbon rail 177 gms
The Forma has a pronounced dip as viewed from the side which means it provides a stable platform with excellent rear of pelvis support for riders who can rotate their pelvis forward well.Ideal nose down angles vary from 2 degrees to 5 degrees depending on the functionality and flexibility of the rider. It is as hard as a Composit but again, the carbon railed version makes it feel almost like a padded seat. I have a number of customers using these who love them but I don’t sell many . The Dynamic below is why.
Dynamic max width 139mm / eff. width 96mm Typical weight: steel rail 252 gms / carbon rail 209 gms
This is my favourite seat in the SMP range. It is a Forma with a thin layer of firm padding. For performance riders there is enough padding to take the edge off the bumps and in other regards, it is everything that a Forma is but with the addition of some padding. Many people who otherwise would use a Forma but baulk at the thought of an unpadded seat choose the Dynamic as a safer option. Much as I like my Composits, the Dynamic, which along with the rest of the Forma Family were not available at the time the Composits hit Oz, would be my first choice of SMP seat if I was in the market now. I have used these seats on male riders from 5’7″ / 170cm and 55kg / 121lbs to 6’4″ /193cm and 108kg/ 237lbs and wildly differing degrees of functionality and flexibility without problems. Just a great all round seat for performance riding.
The Dynamic is best used at a level between 2 degrees down and 5 degrees down at the nose.
Lite 209 max width 139mm / eff. width 102mm Typical weight; steel rail 330gms / carbon rail 287 gms.
Don’t ask me why this is called a Lite 209 because I don’t know. It isn’t light and I don’t know what 209 refers to. The simple explanation is that this is a heavily padded Dynamic and suits a similar activity profile. Even with the padding it maintains a similar deeply curved profile as viewed from the side but the padding widens the effective seat width by lessening the rate of tumblehome. I use the 209 for heavier riders, endurance riders, Mtb XC riders and a lot of women. I’ve got one gent running around happily on a 209 who is 197cm / 6’5 1/2″ and 120 kg / 262lbs and he hasn’t broken it yet.
Full Carbon Lite max width:130mm / eff. width 92mm Typical weight 125 gms.
Basically a skinnier, lighter Forma. Very little give in the shell but good shock absorption from the rails to the point where with knicks on, it almost feels padded. Can be positioned between 2 and 5 degrees down at the nose for best results. One for the lightweight junkies but much more comfortable that it appears at a glance.
I call the seats below orphans because they all use different shells and are not variations of padding based on a single shell.
Glider max width 136mm / eff. width 110mm Typical weight: steel rail 280 gms/ carbon rail 235 gms
The Glider is flatter across the rear than say, a 209 and wider through the centre with less dip in the profile as viewed from the side. It is an ideal seat for moderately large or heavy men or women who ride in a more upright position. I tend to fit these to flat bar city bikes and road bikes for largish people of less than good flexibility. The Glider is also a good choice for MTB riders. It is best used at a nose down angle of anywhere from level to minus 3 degrees. .
Pro max width 152mm / eff. width 103mm Typical weight: steel rail 343 gms. I’ve never seen a carbon railed version, though they are available.
The Pro is kind of interesting. It is a large, long and wide heavily padded seat for large heavy riders, but as you can see from the pic immediately above, the effective width that can be sat on is quite narrow as the the tumblehome is very steep where it drops to the edge. I’ve always been mystified by this shape but have found it to be a good seat for taller, heavier riders who don’t have very wide pelvises. Large, skinny skeletoned people who carry a bit of weight seem to find it ideal. Best fitted to comfort bikes and road bikes for recreational riders of that size and morphology. Nose down angle range that suits best is from level to minus 3 degrees.
Chrono max width 122mm / eff. width 95mm. Typical weight: steel rails 210 gms. There is no carbon railed option
This is SMP’s take on a TT seat. In modern terms that means a seat with a length that is the minimum necessary to ensure UCI compliance. Most TT seats of this type are designed to keep the UCI happy while allowing the rider to effectively sit further forward than would otherwise be possible. The Chrono will allow this compared to the rest of the performance SMP range, but not when compared to other TT seats. The reason is that like all SMP’s the shoulders of the Chrono are much further back towards the rear than is common on other brands. Translation: the rider sits further back relative to the length of the seat than they would on say an ISM Adamo or similar. Much further back. So if you want to sit forward UCI legally, this is not your best option. The other issue with the Chrono is the the deep dip in the profile as viewed from the side. This is similar to the Forma Family, in fact the Chrono can best be described as a scaled down Forma. This presents a problem for anyone approaching an slightly small to average size human. The shorter front to rear length of the dip means that a female riders vulva or the area just behind a male users scrotum gets jammed hard into the rise towards the nose. Basically, the dip is too short for anyone other than children and very small teenagers. There is a market for this seat but it is not for anyone of even average size in either gender. Tiny people only need apply.
Avant max width 153mm / eff. width 135mm Typical weight: steel rails 367 gms. I have never seen a carbon railed version, though they do exist.
The Avant is SMP’s vision of a high quality, large well padded comfort seat for large, well padded men and women. For the right rider, this is a great seat designed for an upright position, usually on a flat bar bike. I’ve had many heavy women and some heavy men who despaired at ever finding a comfortable seat and who found Nirvana on an Avant. Best used at an angle from level to minus 3 degrees. This has become my first choice of seat for the right kind of fit client. If is flat in profile across the rear and offers good support for bones and flesh when there is plenty of both. The width of the centre channel cutout is the widest of the SMP range. Many readers rider performance bikes and laugh at seats like this. Don’t. They have their place and have enhanced the cycling experience for many. The more bums on bikes of whatever type, the better a place the world will be.
I hope this have given you some insight into SMP seats; or at least, my take on SMP seats. Here is a link to SMP’s Seat Selection Table. My experience is at odds with SMP’s suggestions for Chrono, Evolution and Stratos but similar to their recommendations on other seats. A simple and useful guide. Also worth reading is some of the other info on their site as it is more comprehensive than that offered on the sites of other seat manufacturers in the areas that count. Click on http://www.smpselle.com/smp4bike/en/support/selection-table and then look at the Ergonomy and Support tabs.
I’ve also got to mention that I have no connection with SMP, nor have I been offered or accepted any inducements. They are just the brand of seat that helps solve a lot of fitting problems, whether it be comfort, or just as often, an inability to allow a rider to sit back far enough.
Addendum: Instructions for changing seats
1. Lock up the bike in an indoor trainer and use a carpenter’s level to make sure that the bike is leveled between axle centres. This is important as everything you do will only be accurate if the bike is level and stable. In addition to the carpenters level, you will need a steel rule 300 mm long and a marker pen
2. Measure the flat section of the seat rail and use the marker pen to mark the midpoint in the length of the flat section
3. Measure from the flat section to the top of the seat directly above the point you have marked at the midpoint of the seat rail. Record that measurement as seat depth
4. Lay the new seat upside down on top of the old seat so that the curves forward of the seat shoulders match up as closely as possible. The seat shoulders are the most forward part of the widest part of the rear of the seat. The curves are where the seat narrows as it comes forward from the shoulders. Match up the profile of the curves as best as can be done.
5. Note whether the nose of the new seat layed upside down on the old one is forward or rearward of the nose of the old seat currently fitted. Record the difference as seat nose difference. A plus number means that the new seat’s nose is forward of the old seat. A minus number means that the new seat is rearward of the old one.
6. Measure from the centre of the bottom bracket (centre of rotation of the cranks) to the top of the old seat fitted to the bike. Make sure that the measuring edge of the tape passes through the mark on the midpoint of the seat rail. Record that measurement as seat height.
7. Measure from the tip of the nose of the old seat to the back of the handlebar. Make sure that the front wheel is facing straight ahead. Record this measurement as nose to handlebar
8. Remove old seat and fit new seat. Make sure that you mark the midpoint of the seat rail. Fit the new seat at the same seat height as the old seat making sure that you measure seat height in the same way. Look at your seat nose difference measurement. If it is a plus number, move the new seat so that it’s nose to handlebar measurement is that much less than that of the old seat. If it is a minus number, make sure that the new seat’s nose to handlebar measurement is that much more than that of the old seat.
9. Recheck seat height and then recheck nose to handlebar distance. This is as close as you will get by measurement. Any further adjustment must be done by feel. This method will only work as accurately as the measurements you take. Even then, I am relying on you to have enough awareness of how you normally feel when pedalling to recognise that feeling when you duplicate it on the new seat.
Note: Often, more specific answers to your questions can be found in the Comments below or in the eBooks section and FAQ page.
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