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Discussion Starter · #1 ·
Hey guys,

Just wondering, given a bike from the same manufacturer in a large and a medium and the use of stem length to make both set ups the same, would I notice any real difference in handling? I am not a racer, just an enthusiast so it is not win or lose a race kind of thing.
 

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Would rather have the longer TT, shorter stem. The more weight that is out, over the front wheel the less stability IMO.
 

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spadmike said:
Hey guys,

Just wondering, given a bike from the same manufacturer in a large and a medium and the use of stem length to make both set ups the same, would I notice any real difference in handling? I am not a racer, just an enthusiast so it is not win or lose a race kind of thing.
I prefer a moderate length TT and longer stem. I am better able to shift my weight distribution for different situations and the more forward position relative to the front wheel gives me better cornering bite. In most conditions being able to easily weight the front wheel helps it track and grip better for increased control. Still able to shift rearward when needed.
 

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spadmike said:
Hey guys,

Just wondering, given a bike from the same manufacturer in a large and a medium and the use of stem length to make both set ups the same, would I notice any real difference in handling? I am not a racer, just an enthusiast so it is not win or lose a race kind of thing.
Short answer, yes. Flat ground may not be very noticeable. Turns, climbing and descending will be different. From my experience, too long a stem makes a bike prone to endo on the descents. Too short a stem makes it prone to wheelie on climbs. A stem length around 110 works best for me all around. I'm sure there is some personal preference in this. If I had to err on one side or the other, it would be a short stem.
 

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Discussion Starter · #5 ·
I debating getting a smaller size Mach 429, but am wondering if it is worth the money to do so. Technically I should be on a small but have the medium. The difference of top tube is an inch. Therefore, the original question.
 

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Don't forget you can also take up the difference using seat posn[ 429 has moderate seat angle] which has less effect on your handling.Longer stems and shorter wheelbase are good for singletrack carving. Shorter stems and longer wheelbase give more confidence downhill. If you are marginal between sizes, a bigger bike with longer wheelbase will probably be more noticeable difference in handling than tweaking stem and seat posn on a smaller frame. Probably more so on a 29er. But then again don't shoe horn yourself in to a too short a frame size. You can adapt to handling differences of a longer bike but being uncomfortable or unstable isn't much fun and can also unbalance your suspension.
 

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gvs_nz said:
Don't forget you can also take up the difference using seat posn[ 429 QUOTE]

I have seen people state this now way too many times. Seat positions should not be changed to adjust cockpit length. Yes, seat angle may mean you have to adjust the fore/aft of the saddle, but your position should be the same no matter what bike you are on. If you had a Fit Stick you would ideally have all your bikes setup the same within a couple mm when it comes to knee and hip position.
 

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offrhodes42 said:
gvs_nz said:
Don't forget you can also take up the difference using seat posn[ 429 QUOTE]

I have seen people state this now way too many times. Seat positions should not be changed to adjust cockpit length. Yes, seat angle may mean you have to adjust the fore/aft of the saddle, but your position should be the same no matter what bike you are on. If you had a Fit Stick you would ideally have all your bikes setup the same within a couple mm when it comes to knee and hip position.
What's a Fit Stick?...presuming it an adjustable template...can you show us?

OP...ideally you need to know your best combined tt length and stem length.
Best fit if standover isn't an issue is to buy a bike with a stem target of 100-110.
Norminal stem length is about adjustability up and down and why manufacturers sell bikes with this size at about the nominal. For example...I ride a 130mm stem with my current 29er. That said, I don't do BIG descents and I ride with a riser bar which changes tendency to endo. I do not have ANY fear of going over the bars with my set up because my weight is still well back with a high bar.
The only way to learn best fit is thru trial and error and honestly making fit mistakes that you fix with your next bike. After a couple of bikes, if you are a student of fit, you should be able to dial in what works best. For example, my next 29er will likely be a XL which will put me on a stem length of 110mm or so...but will challenge my standover a bit more. I opted for my setup because I prefer the smaller frame size large for standover. The issue is if you size too small is, you run out of stem length options. I did have a 140mm stem on the bike for a short period tho to see if I preferred to be even more stretched out which I don't.
PS: I don't buy into all the fashionable arguments here against long stems. Years ago long stems were popular on mtbs and never did fall out of favor on road bikes. Some of the fastest mtb'ers I know still ride with a long stem including some pros to minimize frame size and still achieve adequate cockpit length for power.
PS: personal bias comes into play when it comes to fit and one of the reasons I believe there to be such divergent opinion. Me for example...I have long arms so my torso CG is still well back even with a long stem. Perhaps the comments from those about long stems creating endo problems are real...for their body type. Their related position on the bike may indeed promote a weight forward position so arm length maybe should be considered for stem length as well.
 

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offrhodes42 said:
gvs_nz said:
Don't forget you can also take up the difference using seat posn[ 429 QUOTE]

I have seen people state this now way too many times. Seat positions should not be changed to adjust cockpit length. Yes, seat angle may mean you have to adjust the fore/aft of the saddle, but your position should be the same no matter what bike you are on. If you had a Fit Stick you would ideally have all your bikes setup the same within a couple mm when it comes to knee and hip position.
I agree if you are on a road bike or xc race bike which generally aim to get knee bb relationship the same. In case you haven't noticed ride bike and xc race bike seat angles are very close. Across the board MTB seat angles vary from 72 right up to 74.5 and that's not a custom fit for femur lengths. On a mtb you are up and down out of the saddle, or bouncing around, all the time so the knee bb relationship comes in to play mainly when climbing. In which case you can slide fwd on the nose of the saddle.So, sure, if you are xc racing then look to keep BB/ seat relationship the same at the expense of bike handling. XC racing is all about the climbing. On the way down you try not to loose posn you gained going up. Not many chances to pass going down xc racing.

I must have had 30 plus bikes over the years. If I'd stuck to the, std bike shop i'll get sued if you get sore knees rule, I would have been limited to xc race bikes, 29ers or be running 150mm stems on bikes with 72 degree seat angles. If mtb mfg stuck to the same rules all their bikes would look like variants of road bikes. aka mtb's 25 years ago.
 
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