XC Stem Length and Bike Sizing

[k3n!f]

Hey all, I'm thinking about getting a shorter stem as my bike is slightly to big for me and my stem is currently 100mm. Just looking for some opinions on running a shorter stem on a XC bike. Opinions on a 90mm/80mm/70mm stem on a XC hard tail?

Also if anyone can be bothered, can you post your specs:

Bike: Yeti ARC
Size: Large
Rider height: 181cm
Effective top tube: 610mm
Stem length: 100mm
Handlebars: 1" rise 615mm

I am trying to solve my long term lower back pain after riding for >1 hour, despite good core body strength. I found a fantastic bike fitting spreadsheet that is telling me I should have a 76mm stem, which might explain my sore back. Here is the link to the spreadsheet for those interested:

http://weightweenies.starbike.com/forum/viewtopic.php?f=8&t=51071

Thanks for your help

 

[nickhagee]

my personal opinion is that you go with what you find comfertable
im getting a new stumpy (m) in 1 or 2 weeks and am going to swap the stem for a 60mm straight away (yes i have ridden one with the stock stem length) because i prefer to have my hands not so far in front of the wheel
my 2c

 

[chops007]

at my lbs they have a bikefit system were they film you riding and with there program on the computer they use they tweak your set up with all sorts of measurements..

check out an avanti plus bike shop is my tip..

 

[mushroom]

Speak to the shop you bought the bike from (or else, another shop) about trying various stems. Stem size is a big part of bike fit and really should have been sorted out when they sold you the bike.

Start with an 80cm stem based on your fit spreadsheet and go from there.

 

[akashra]

I had to drop my Anthem (M) back to a 90mm stem, and that made a massive difference - bike certainly feels heaps twitchier and doesn't climb as well, but I can descend way better. Similarly I switched my hardtail from a 105mm to 100mm stem and that certainly helped a bit.

Certainly give it a try, just make sure you give yourself time to get used to the quicker turning and reduced precision.

 

[Grover]

I'm 182cm. When I owned a Yeti ARC I rode a Medium with a 120mm stem. If I rode a Large that would equate to a 85mm stem. I do have a long torso that means I usually run a longer than average stem.

If you're of average proportions the fit that you've got from the spreadsheet sounds pretty spot on from my experience. I've previously run my numbers through that spreadsheet to see how accurate it was, the numbers it gave me were what my continual tweaking had eventually landed on. Definitely try its recommendations, if anything they're a good place to start from in finding your proper fit.

As an aside, what frame size/top tube length did the spreadsheet recommend? I'd be guessing it was smaller than what you're currently using.

 

[bazza]

awesome! i really need to get my sizing issue sorted on my mtb after so long of putting it off. i always forget, do a race, get crippled by my lower back.

 

[BT180]

I had the same lower back problems. Went to my lbs for a proper bike fit (ended up with a longer stem) and the pain is now gone.

Get a professional bike fit done - it's the only way to be 100% sure. I can't recommend it enough.

 

[Turner_rider]

Hey all, I'm thinking about getting a shorter stem as my bike is slightly to big for me and my stem is currently 100mm.

Ken,

Based on seeing you ride I actually think you bike is the right size for you - well the frame is.

You could go to a shorter stem say 90mm and see how that goes or maybe even look at the number of spacers you are running under your stem.

I know that you say you have good core strength, but there is also a simple back excercise which i was shown years ago which may also work wonders for you.

 

[a_hargy]

I know that you say you have good core strength, but there is also a simple back excercise which i was shown years ago which may also work wonders for you.

Care to share which back exercise that is mate?
I used to have lots of trouble with my back, a lot of which was likely associated with my bad hamstrings (torn 3 times in 2 years playing footy). I started stretching my hamstrings, glutes and hip flexors a lot more which helped to free up my back but it still gets very tight towards the end of a ride.

 

[k3n!f]

Thanks very much for the replies guys, extremely helpful I have borrowed a 90mm stem (from my girlfriends bike) to try for the week to see if that improves things for me. Essentially I am looking for some assurance that putting a short stem on a XC hard tail won't bugger up the handling/weight distribution too much.

Stem size is a big part of bike fit and really should have been sorted out when they sold you the bike.

The frame was bought here on farkin and the parts came from my previous hard tail which was slightly smaller. I bought the frame because it was brand new, but sold due to injury, so I got $600 off. Unfortunately I fit slap bang in the middle of Yeti's sizing charts for medium vs large.....

I'm 182cm. When I owned a Yeti ARC I rode a Medium with a 120mm stem. If I rode a Large that would equate to a 85mm stem. I do have a long torso that means I usually run a longer than average stem.

As an aside, what frame size/top tube length did the spreadsheet recommend? I'd be guessing it was smaller than what you're currently using.

Mmmmm I have long legs and arms, but a relatively short torso. I thought the long arms thing would make up for the short torso in terms of cockpit length, but that spread sheet has got me thinking about getting my bike set up properly to stop my constant back pain.

The spreadsheet recommends a size 19.4 bike with a cockpit length of 54.1cm with flat bars. The stem length it recommends is 7.6cm, but I thought an 80mm one would be better because I have riser bars. Can you remember what the spreadsheet recommended for you?

awesome! i really need to get my sizing issue sorted on my mtb after so long of putting it off. i always forget, do a race, get crippled by my lower back.

Mmmm same here. Back pain is the limiting factor in my riding. If I want to do a 2 hour XC race I have to allow 1-3 days afterward to not be able to walk properly, and at least a week before I'm riding hard again. I really paid for a recent enduro race where I rode 6+hours and 90+km....

Ken,

Based on seeing you ride I actually think you bike is the right size for you - well the frame is.

You could go to a shorter stem say 90mm and see how that goes or maybe even look at the number of spacers you are running under your stem.

I know that you say you have good core strength, but there is also a simple back excercise which i was shown years ago which may also work wonders for you.

Mmmm I would have thought the same Andrew, and the bike has always felt comfortable when I get on it straight away, it just seems to be the longer/harder rides that give me grief. The group Cyclingo rides are fine because they stop every 15 minutes giving me a chance to stretch and rest for a while.

I'm very interested in this back exercise of yours, can you explain it or do I need to see it in person?

 

[Turner_rider]

Mmmm I would have thought the same Andrew, and the bike has always felt comfortable when I get on it straight away, it just seems to be the longer/harder rides that give me grief. The group Cyclingo rides are fine because they stop every 15 minutes giving me a chance to stretch and rest for a while.

I'm very interested in this back exercise of yours, can you explain it or do I need to see it in person?

I had the problem for ages until I was showed the excercise in question and I haven't had a problem since. In fact it wasn't until after several hours hard riding soon after starting the excercise that I realised "Hey my back doesn't hurt!"

I could try and explain it but its easier to show you next time you are in West Hobart. Given it takes a total of 10 minutes a week to do its a relatively simple fix if it works for you.

 

[offthepace]

Hey all, I'm thinking about getting a shorter stem as my bike is slightly to big for me and my stem is currently 100mm. Just looking for some opinions on running a shorter stem on a XC bike. Opinions on a 90mm/80mm/70mm stem on a XC hard tail?

Also if anyone can be bothered, can you post your specs:

Bike: Yeti ARC
Size: Large
Rider height: 181cm
Effective top tube: 610mm
Stem length: 100mm
Handlebars: 1" rise 615mm

I am trying to solve my long term lower back pain after riding for >1 hour, despite good core body strength. I found a fantastic bike fitting spreadsheet that is telling me I should have a 76mm stem, which might explain my sore back. Here is the link to the spreadsheet for those interested:

Thanks for your help

Have tried that spreadsheet and the measurements it gives me are a good bit out from a bike fit I had. Best to get a good fit done if your having problems from that short a ride, which will take into account more than 2 measurements. I had minor lower back problems in the past which arose from to much saddle set back.

 

[karl_eller]

Thanks very much for the replies guys, extremely helpful I have borrowed a 90mm stem (from my girlfriends bike) to try for the week to see if that improves things for me. Essentially I am looking for some assurance that putting a short stem on a XC hard tail won't bugger up the handling/weight distribution too much.

I've had similar problems (although for me it was neck/shoulder pain), and playing around stem length and rise helped a fair bit. If you're stretched out too much, a shorter and/or higher stem even just a small amount will most likely help a fair bit (for me, changing from a 100mm to 80mm made a massive change). Only down side is that a shorter or higher stem will make climbing a little harder, but on the plus side descents will be a bit easier. Steering will also be slightly more twitchy, but aside from that it should handle fairly much the same.

Eller

 

[k3n!f]

I had the problem for ages until I was showed the excercise in question and I haven't had a problem since. In fact it wasn't until after several hours hard riding soon after starting the excercise that I realised "Hey my back doesn't hurt!"

I could try and explain it but its easier to show you next time you are in West Hobart. Given it takes a total of 10 minutes a week to do its a relatively simple fix if it works for you.

Hmmm this sounds very promising indeed. Are you likely to be attending any Cyclingo group rides in the next few weeks/months?

I just found this on bikeradar.com:

http://www.bikeradar.com/fitness/article/health-lower-back-pain-22293

I will persist with the 90mm stem for a while and see if I like it, but I think I really probably do need the 80mm stem.

Thanks for you help everyone

 

[Grover]

Mmmmm I have long legs and arms, but a relatively short torso. I thought the long arms thing would make up for the short torso in terms of cockpit length, but that spread sheet has got me thinking about getting my bike set up properly to stop my constant back pain.

The spreadsheet recommends a size 19.4 bike with a cockpit length of 54.1cm with flat bars. The stem length it recommends is 7.6cm, but I thought an 80mm one would be better because I have riser bars. Can you remember what the spreadsheet recommended for you?

Have tried that spreadsheet and the measurements it gives me are a good bit out from a bike fit I had. Best to get a good fit done if your having problems from that short a ride, which will take into account more than 2 measurements. I had minor lower back problems in the past which arose from to much saddle set back.

I should probably clarify. The measurements the spreadsheet spat out is what makes me comfortable no matter what I've been doing off the bike or what shape I'm in. It is designed to quickly fit riders so they'll be comfortable which it does very well. It's a recreational fit.

For interests sake my inseam is 840mm, elbow-middle finger is 480mm and flexibility 7. Shoe size 45, saddle length 278mm. The mtb measurements I get are 18.5" frame, 54.5cm saddle nose-bars, 7.4cm saddle-bar drop.

My preferred setup is a cockpit length 2cm longer than this, I'm faster and like the handling of the bike better. Like you though my back can be crippled after a 2hour XC race IF I haven't been stretching and doing core work. The spreadsheet isn't a be all and end all, but a good place to start for someone that just wants to ride their bike comfortably.

Funny that your current cockpit length is within 5mm of my preferred cockpit length and it cripples both of us. Do some stretching and core work and you should be able to ride that position comfortably. While you're progressing your flexibility and core strength I'd say go with what the spreadsheet suggests for cockpit length.

Disregard the stem length recommendations as it doesn't make sense for them to change as to what setback your seatpost is. Your seat should be in the same position no matter the setback of the seatpost. Set the saddle up in the correct position behind the bottom bracket, then measure the cockpit length and calculate the required stem length. I think you'll find the stem length you require is shorter than the spreadsheet recommends as your top tube is longer than would be on an average 19.4" frame.

 

[drasnian]

Core strength exercises may or may not help with a sore lower back on long rides.

If you're flexible then i suppose a sore lower back could be result of a weak core not being recruited properly when you maneuver the bike, especially when lifting the front wheel.

If you could be more flexible, then work on your flexibility. A 100mm stem is not long for someone your height. But if that hasn't worked, i guess you need a shorter one!

 

[climbo]

trial and error is the only way, go for more rise on your stem maybe? You'll get a shorter cockpit and be more upright too. Computer modelling, recommended bike fitters (or sponsors) and one fits all spreadsheets are only good for so much, you still need to interpret them to fit your own needs. So many factors go in to fit and eliminating problems, one change in stem might do the trick if you're lucky.

 

[k3n!f]

First off I changed the 100mm stem to a 90mm stem, but found no real reduction in my back pain ~7/10 riding induced back pain points.

I decided I would change the entire setup to try to get as close to the spreadsheet's recommendations*. This involved moving the saddle up by 25mm(!), dropping the stem by 10mm and moving the seat back 10mm. First off, despite these measurement seeming counter productive for someone with back pain, the pain actually decreased (down to 4-5/10 riding induced back pain points). I think I will try to borrow an 80mm stem from my LBS to try it out and see if the pain reduces further.

*The spreadsheet recommends 8.9cm of saddle setback. This is completely impossible with my setup as I would need a setback seat post. I decided that my Gobi saddle was probably long in the nose, and that as my torso is relatively short, I would use a lower measurement then recommended. I settled on 6.0cm of setback, which still allowed me to maintain my ~54cm cockpit. When I get an 80mm stem I will hopefully be able to move the saddle further back to get closer to the recommendations.

How much saddle setback does the spreadsheet recommend for you Grover? How much do you actually run?

For interests sake my inseam is 840mm, elbow-middle finger is 480mm and flexibility 7. Shoe size 45, saddle length 278mm. The mtb measurements I get are 18.5" frame, 54.5cm saddle nose-bars, 7.4cm saddle-bar drop.

My preferred setup is a cockpit length 2cm longer than this, I'm faster and like the handling of the bike better. Like you though my back can be crippled after a 2hour XC race IF I haven't been stretching and doing core work. The spreadsheet isn't a be all and end all, but a good place to start for someone that just wants to ride their bike comfortably.

Funny that your current cockpit length is within 5mm of my preferred cockpit length and it cripples both of us. Do some stretching and core work and you should be able to ride that position comfortably. While you're progressing your flexibility and core strength I'd say go with what the spreadsheet suggests for cockpit length.

Disregard the stem length recommendations as it doesn't make sense for them to change as to what setback your seatpost is. Your seat should be in the same position no matter the setback of the seatpost. Set the saddle up in the correct position behind the bottom bracket, then measure the cockpit length and calculate the required stem length. I think you'll find the stem length you require is shorter than the spreadsheet recommends as your top tube is longer than would be on an average 19.4" frame.

Your last paragraph is right on the money, if I run the correct setback I will need a new seat post and a 50-60mm stem. Considering your taller than me, but my leg length is 88cm (4cm longer) I think the setback the spreadsheet is recommending is too long for my shorter torso.

I am really happy with the increase in saddle height. I was really skeptical about raising my saddle by 25mm but it felt fantastic. I didn't feel like it was too high, and I got heaps more power while seated. I am yet to take it down something steep yet though, I have a funny feeling that increase in height is going to make steep descents a little more interesting....

 

[Grover]

Saddle setback for me was 79mm. It has more of a correlation to your leg length than your torso length. Don't go slamming it all the way back straight away but work your way back there to try it. It's going to mean a pretty short stem. If that gets you comfortable though so be it and consider a shorter top tube in your next frame.