Stem length

[RobertWhitehead]

Good morning all

 

I'm sitting with a wee problem and really need some guidance on this. I've got two bikes that I've been using, a 26er and a 29er. I put something like 8000km onto the 26er and then converted it to a single speed. I loved it but after breaking my second tensioner I decided to hang up my ss shoes and change it back to a 1x9. 

 

On the 29er side, I built it up from scratch for the 2015 Transbaviaans cause I found my friends were much faster than me on the 26er ss. Now to try not make this too "long winded" I will give the facts and move on 

 

My 29er has a top tube length of 610mm along with a 60mm stem = 670mm 

My 26er has a top tube length of 550mm along with a 90mm stem = 640mm

 

Now I honestly believe that the 29er sucks and I struggle my ass off to get any rhythm on it. I'm still under the impression that my "overall" average on the 26er will be higher than on the 29er and I will not feel sooo tired once I get off the 26er than when I get off the 29er. 

 

Will changing the stem length down from a 60mm to a 40mm or so improve my position and provide me with a better rhythm or not at all? I will be upgrading to dual sys in the new year (got a herniated disc in my back) but I need to decide which bike to use for the 94.7

 

Thanks in advance

[Skinnyone]

IMHO - yes it will help

 

And no harm in trying either...

[Captain Fastbastard Mayhem]

Yes, it will bring your hands closer to you and therefore mirror the amount of "reach" (not actually reach, but you know what I mean) from the saddle to the bars, thereby making you more upright in your positioning. I'm of course assuming that your saddle positioning is exactly the same between the 2 bikes in terms of distance above and behind the BB. If not, get that sorted before you make any changes to the stem. 

[RobertWhitehead]

Thanks guys, I've had a set-up done on the 29er and the position of the saddle is the same as on the 26er (part from the top tube length that is) 

[bikebloke]

a 40mm stem will make your steering very twitchy

stem length should be more about control than fit on an mtb (or am I wrong)

[Captain Fastbastard Mayhem]

a 40mm stem will make your steering very twitchy

stem length should be more about control than fit on an mtb (or am I wrong)

Yes and no. Stem length can be used to fine tune fit, within reason. 

[RobertWhitehead]

Yes and no. Stem length can be used to fine tune fit, within reason. 

 

So the 20mm drop from a 60mm to a 40mm will fall within the "within reason" category then? 

[Captain Fastbastard Mayhem]

So the 20mm drop from a 60mm to a 40mm will fall within the "within reason" category then? 

Yep. Reason I say that is cos there's generally 20-30mm difference in reach / top tube between frame sizes. And unless there's a mahooosive 100mm tiller on the bike as standard, a 20mm drop would be seen as reasonable. If there IS a mahooosive 100mm tiller on the bike as standard, and it's the right size frame, a change as much as 60mm could be considered reasonable. 

[Johan_Kleynhans]

I am in the opposite situation.

 

I have a 90's 26" mountain bike which is as close as I could get to my roadbike in terms of the distance between the handlebar grips and the back of the saddle. The saddle BB position is the same on both bikes.

 

In December I bought a 29" and started by getting the saddle BB measurements exactly the same. There is however a massive discrepancy on the measurement from back of the saddle to handlebar (120mm).

 

I understand (and have not done any races with the new bike yet) that you sit more upright on the mountain bike versus the roadbike. I feel cramped on the bike however as I want to get into a more aero-dynamic position but cannot. I have lowered a the handlebars as much as I could by removing the spacers and turning the the stem around.

 

Can I install a longer than standard stem and what will be the effect off road? I favour more the jeep track type of roads rather than the tight bits.

 

Thanks

 

Johan

[BaGearA]

I am in the opposite situation.

 

I have a 90's 26" mountain bike which is as close as I could get to my roadbike in terms of the distance between the handlebar grips and the back of the saddle. The saddle BB position is the same on both bikes.

 

In December I bought a 29" and started by getting the saddle BB measurements exactly the same. There is however a massive discrepancy on the measurement from back of the saddle to handlebar (120mm).

 

I understand (and have not done any races with the new bike yet) that you sit more upright on the mountain bike versus the roadbike. I feel cramped on the bike however as I want to get into a more aero-dynamic position but cannot. I have lowered a the handlebars as much as I could by removing the spacers and turning the the stem around.

 

Can I install a longer than standard stem and what will be the effect off road? I favour more the jeep track type of roads rather than the tight bits.

 

Thanks

 

Johan

Setback seatpost is all i can think of

[Johan_Kleynhans]

I want to avoid that if I can.

 

In a different topic we were discussing knee problems. I normally don't mess much with saddle position in relation to the BB.

 

I had my saddle back as much as I could (20mm) a while back to increase the distance to the handles and when I go hard I felt my knees. I am used to my roadbike set up which I used all my life. I moved it the saddle back to the position I like.

 

So I need to try something else.

 

Thanks in any way.

 

Johan.

[Captain Fastbastard Mayhem]

You're on the wrong size frame, quite simply.

[Captain Fastbastard Mayhem]

And yes, you're right. You don't want to affect the BB/saddle geometry. That should be the same across your bikes except TT bike.

 

You need a longer frame. Putting a longer stem on it will work, but it will affect the handling negatively, especially at speed.and in the technical bits.

 

Also. Try a wider bar. What size bar do you have any the moment? Going wider will give you more space to deal with. Also. Mtb stance is mostly with slightly bent elbows and a relatively flat forearm vs road where your arms aren't quite as bent. If you're locking your arms your "stance" is incorrect

 

But. Go for a fit. They'll most likely tell you that your frame is too small for you.

 

Mtb is not road.

[Johan_Kleynhans]

Sorry for only replying now. Thanks for all the input.

 

I have measured the stem from the centre of the handlebar to the centre of the neck (where it attaches to the forks) and the length is 95 mm. Handlebars is 740 wide.

 

I had myself measured at a few different bike shops and based on the tables I should be on a medium. That was the recommendation of all of them.

 

I have an Anthem and if I am not mistaken the large's top tube is only 1 cm longer.

 

My arms are reasonably bent and my forearms reasonably flat when I cycle fast. I am on tar probably 85% of the time.

 

Thanks

 

Johan

[Blackheart]

You're on the wrong size frame, quite simply.

This is probably the case

[Captain Fastbastard Mayhem]

Sorry for only replying now. Thanks for all the input.

 

I have measured the stem from the centre of the handlebar to the centre of the neck (where it attaches to the forks) and the length is 95 mm. Handlebars is 740 wide.

 

I had myself measured at a few different bike shops and based on the tables I should be on a medium. That was the recommendation of all of them.

 

I have an Anthem and if I am not mistaken the large's top tube is only 1 cm longer.

 

My arms are reasonably bent and my forearms reasonably flat when I cycle fast. I am on tar probably 85% of the time.

 

Thanks

 

Johan

How tall are you. And no. A large anthem has a top tube 0.8" longer than a medium. That's 20mm.