bike fitting and stems

davidwilcock

Hi

I have a bike which I think is a little small for me. I'm 180cm with an 80cm inside leg (no other measurements to hand)

The bike is a c2011 Allez in size 54.

My 'posh' bike is a wyndymilla massive attack with a 59cm top tube. This feels great on drops and hoods and I could ride it all day. With the Allez I notice some lower back pain.

Ive come to the conclusion that I have a long torso for my height and need a long top tube to go with it. Rather than going to the expense of a new commuter I was thinking I could replace the 110mm stem with a 140mm stem as a starting point

Is my top tube assumption corrrect and Is this stem plan a good idea or just wont work?

diamonddog

What length is the tt on the Allez?

cyclenutnz

You need to figure out the bar XY of your wyndymilla. Is it an R2R or custom? If custom do you have the drawing? Whether custom or R2R - what is the stem length and spacer height (frame to bottom of the stem)?

Or you could measure both bikes.
Stick the back wheel against a wall and measure wall to BB and wall to bar centre (horizontally with bike perpendicular to wall). Then vertically floor to bb and floor to centre of bar. The differences give you bar X and bar Y from BB.

That will tell you exactly what the difference in reach or height of the bars is. Possibly with a need to factor different bar reach if you don't have the same model on each bike.

daniel_b

I think you are on the right lines.

I am the same height as you, but have an 86.4cm inseam, and consequently a much shorter upper body than you.

I ride 54's with 545 top tubes (I suspect your Allez has a top tube in the vicinity of this measurement), and 90mm stems.

I used to have the reverse issue though, a bike that was too big, with too long a stem as well - took me a while to figure that one out, early days of riding.

59 is a long top tube to me, but if that means you are comfy, then seems a logical, and cheap place to start, and will also not alter your position over the pedals - assuming that is optimum to start with.

Another option, on top of, or as well as the longer stem, is to buy a more offset seatpost, and or trial it by sliding the seat further back to start with, although as mentioned it will alter your postion related to the pedals.

140mm stems are not the norm, so if you are after a second hand bargain, you may have a bit of a wait on your hands.

davidwilcock

That's really helpful guys thanks. I think the WM is a standard size XL (I bought it second hand). I'll make some measurements this week.

I think the top tube is 545 on the Allez

I do ride with a short stem on the WM which I really like for some reason. I was a little concerned that a 140mm stem might make the handling a little twitchy?

diamonddog

IME a longer stem makes the front end a bit more stable, my suggestion would be try the longer stem as a start point.

birdie23

Daniel B wrote:

Another option, on top of, or as well as the longer stem, is to buy a more offset seatpost, and or trial it by sliding the seat further back to start with, although as mentioned it will alter your postion related to the pedals.

You should never move your saddle to adjust your reach. Make up the reach difference between the two bikes with a longer stem. Follow cyclenutz advice to match your WM.

As for handling, with a longer stem the bike should be more stable (more weight over the front wheel as the stem gets longer, this is only good to a point of course) and slower because the size of the steering arc changes. So while a short stem may feel and make the bike react like a steering wheel would (twitchier) a long stem will make the bike react more like you are steering using a tiller. Head angle and trail are more important in handling, the stem length just slightly changes the characteristics.

daniel_b

davidwilcock wrote:

That's really helpful guys thanks. I think the WM is a standard size XL (I bought it second hand). I'll make some measurements this week.

I think the top tube is 545 on the Allez

I do ride with a short stem on the WM which I really like for some reason. I was a little concerned that a 140mm stem might make the handling a little twitchy?

How short is the stem on the WM?
Do let us know how you get on

birdie23 wrote:

Daniel B wrote:

Another option, on top of, or as well as the longer stem, is to buy a more offset seatpost, and or trial it by sliding the seat further back to start with, although as mentioned it will alter your postion related to the pedals.

You should never move your saddle to adjust your reach. Make up the reach difference between the two bikes with a longer stem. Follow cyclenutz advice to match your WM.

As for handling, with a longer stem the bike should be more stable (more weight over the front wheel as the stem gets longer, this is only good to a point of course) and slower because the size of the steering arc changes. So while a short stem may feel and make the bike react like a steering wheel would (twitchier) a long stem will make the bike react more like you are steering using a tiller. Head angle and trail are more important in handling, the stem length just slightly changes the characteristics.

But that is assuming that the OP's limb lengths are spot on for the position that his saddle is in currently, which we do not know.
Additionally, the bike could already be fitted with an inline seatpost, unlikely if it's brand new I will admit, but as an example (Although not suggesting the OP would fall into this camp I hasten to add!) my brother in law bought a new shorter stem for his brand new bike, as he said the reach was too far, and wanted me to help fit it.
I went around there, and the first thing I noticed was that the saddle had been slammed all the way back on it's rails :?
No idea why a bike shop would have done that, but there we go.
On top of that, the stem he had bought was oversize, and his bars were 26mm, but that's another story!

Saddles have rails, which gives you a modicum of adjustment, and if that wasn't legit, they would just have one mounting point - imho.
Additionally, the difference in buying an inline, or a 15mm, versus a 30mm setback seatpost, is the same effective change as altering the postion of the saddle on it's rails - well until you figure out what offset you need, so you can get the right seatpost that is.
I started with an inline on my Scott, and as I became more flexible, slid the saddle back, and then purchased an 25mm offset seatpost instead, and now have the correct setup for my body shape, and level of flexibility.

Not trying to create an argument birdie123, and I am no bikefitter, this is just from my personal experience, but would be interested to hear reasons otherwise - always open to other methods, or rules if you prefer.

One more thing I would say to the OP, and again, no offence meant here, but for ages I was riding on the wrong part of the saddle, too far forward - when I eventually found the wings of the saddle, not only did this make things more comfortable, but also stretched out my position some more, so it could be worthwhile checking how and where you sit on the saddle, and see if it feels right, and maybe try sitting further back not trying to teach you to suck eggs, but it was somewhat of a revelation for me when it clicked.

I have Ariones on all of my distance bikes, so I am at home as soon as I get on, and it's also then easier to replicate setup from one bike to another.

birdie23

Daniel B wrote:

Not trying to create an argument birdie123, and I am no bikefitter, this is just from my personal experience, but would be interested to hear reasons otherwise - always open to other methods, or rules if you prefer.

I'm no bikefitter either, so I could be wide of the mark, but firstly I am assuming his saddle position is optimal to provide a good position to transfer power to the pedals. If this is the case almost everything I have read suggests you then shouldn't change the saddle position to account for reach issues as you will impact on your pedaling motion.

The logic I've most commonly read is 1. sort your saddle position to optimise power transfer, 2. adjust handlebar position (fore/aft, up/down) for reach and back angle.

Edit: Didn't really touch the bit about saddle rails. Basically, they are there to move the saddle position but it's to move the saddle to optimise pedaling motion, not reach.

daniel_b

birdie23 wrote:

Daniel B wrote:

Not trying to create an argument birdie123, and I am no bikefitter, this is just from my personal experience, but would be interested to hear reasons otherwise - always open to other methods, or rules if you prefer.

I'm no bikefitter either, so I could be wide of the mark, but firstly I am assuming his saddle position is optimal to provide a good position to transfer power to the pedals. If this is the case almost everything I have read suggests you then shouldn't change the saddle position to account for reach issues as you will impact on your pedaling motion.

The logic I've most commonly read is 1. sort your saddle position to optimise power transfer, 2. adjust handlebar position (fore/aft, up/down) for reach and back angle.

Edit: Didn't really touch the bit about saddle rails. Basically, they are there to move the saddle position but it's to move the saddle to optimise pedaling motion, not reach.

True enough, I have heard that too, and correct me if I am wrong, but is that normally referred to as KOPS?
If it is, I have also read articles that are of the opinion KOPS is not the final word in saddle positioning, as if I recall correctly, and I'm paraphrasing here, that the method does not take into account when people might have shorter or longer than normal femurs, and or tibia\fibulas - and yes I did have to google to get those
If it isn't KOPS, is there another known method out there that gets used a lot?
Not something I have ever researched much I must be honest.

Having said all that, I am in posession of this book, but do not know what method he uses (It appears to be KOPS!), just know it generally seems to get good reviews, but am open minded and need to give it a go:

And one of these:


That's the goniometer, rather than the leg, as I have two of those.

I really should get reading it, and put it to use, especially as I want to start TT's next year, could yield some extra power even - optimisitc head on
Young family means time to do this is limited, especially as you need someone else in there with you to take measurements etc, I assume so anyway.

Apologies OP, I have tangented somewhat :oops:

birdie23

Yeah, KOPS is one way (though plenty of opponents to that method on here) but I think in general once you have an optimal location for your legs to push the pedals, regardless of how you got there, it would be strange to change it just to adjust reach that is easily adjusted with a stem change (up to a point).

daniel_b

birdie23 wrote:

Yeah, KOPS is one way (though plenty of opponents to that method on here) but I think in general once you have an optimal location for your legs to push the pedals, regardless of how you got there, it would be strange to change it just to adjust reach that is easily adjusted with a stem change (up to a point).

Yep totally agree with that Sir

6wheels

The 'Balance Method' is another way of setting the saddle setback. You should be able to take your hands off the hoods whilst cycling and not fall into the bars ie hold yourself up.

There is a good article on the net, I'll have a look for it tomorrow...dinner time now.

N0bodyOfTheGoat

Slightly going off topic, but why does the UCI(?) stipulate that the saddle nose must be no closer than 5cm vertically to the position of the bottom bracket?

6wheels

Steve Hogg article...

https://www.stevehoggbikefitting.com/bi ... oad-bikes/