 You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
When a manufacturer designs a frame do they start off with a medium frame and base the whole thing around that size then adapt the design for the other sizes, meaning the other sizes could potentially have a poorer performance?
Some makes of frame look very different in different sizes.
Discuss.
I've actually got the same frame in two different sizes (Marin 140). The medium fitted like a glove, looked fantastic and was a hoot to hurl around, but I kept smacking my knees on the bar and had the seat as far back on the rails as it would go. I gave it to Mrs PJM and I bought a size large, which looks gawky, is a tad too tall but just long enough. I've lost a little of the handling finesse but it fits perfectly up front and I can ride it all day without aching anywhere.
Remember that bike manufacturers often use small/medium sizes for publicity shots so large and extra large frames do tend to look ungainly. As for suspension performance, there shouldn't be an issue - many manufacturers change the shock tune for heavier & larger riders and wheelbase aside there shouldn't be any change in how the suspension actually works.
Mm yes. I think it would possibly make more difference with steel hardtails where the geometry and frame construction may have more of an impact on ride characteristics.
one problem is often (with FS bikes) they size the front triangle but use the same rear triangle for all sizes.. so the chainstays etc are proportionally longer on the smaller sizes, so handle quite differently. not all makes do this i guess.
Some manufacturers changing tubing according to frame size.
smiff - Member
one problem is often (with FS bikes) they size the front triangle but use the same rear triangle for all sizes.. so the chainstays etc are proportionally longer on the smaller sizes, so handle quite differently. not all makes do this i guess.
What mfrs use different length chainstays on hardtails?
NONE, as far as I know.
Cube and On One (456 evo) do.
I believe it differs depending on who does the r&d on a bike. If It's a big bloke, then the one that fits him is optimised, the others scaled up or down. If he's shorted, the medium is optimised.
Or so I heard.
2mm between some sizes on the evo.
Less than the wear on a tire.
2mm is enough to make a difference to the balance point of the bike and is the same as moving the saddle forward 8mm. Which makes quite a difference too.
How much difference would you put into a chainstay length change, Mr Al?
And would you make the small ones shorter or the large ones longer.
Al - Norco
So why isn't everyone doing it then?
DH bikes kinda have done for decades with adjustable drop-outs, Al.
Varience in Hardtail chainstay lengths gives differing ride characteristics, I personally wouldn't want anything other than short ( or super short) stays for the way I ride even though I'm well above average height.
Looking at the aesthetics of almost all mtbs I don't think anyone in the bike industry (other than 29er marketeers) really GAF about properly tall riders.
Kinda...
If it made a difference to the average rider, everyone mould be doing it I think.
Oh.. They will at some point, it's just not fashionable yet. 😉
What is "Average" in terms of height, weight and limb length?
I mean I'm 5'10" broadish chest/shoulders, 32" inside leg (I think)...
I find I'm led more by TT length than anything else now, Thus I have various MTB frames with seat tubes ranging from 16" to 19"
😀 extreme.
I'm taller than you (just) and have a 14" seat tube on my most used and most versatile bike.
I choose frames by downtube length. It's the only measrement that makes sense. BB height, HA and stay length are v. Important to me. SA doesn't actually matter too much (unless wildly out) and why ride an 18" seatube with it's reduced standover height and only 200mm exposed seatpost for full leg exension while climbing etc. when 410mm posts are commonplace
What height are you?
Wasn't talking to you Al
No probs shorty 😛
How tall are you GW?
5'11" without shoes on (over 6' in my fav heels)
why is everyone so interested? :/
LOL
To truly equalise performance and feel between frame sizes, travel should be proportionate too.
Tire width too.
But how would you know? Wear stilts and side a bigger bike?
If two people of different heights both rode a drop proportionate to their heights, then surely the angle of rotation of the bike and fork travel proportionate to each persons size should be equal?
That would be the ideal.
Of course, we'd need infinitely variable rim sizes and elasticated tyres 😀
You'd need to tune each individual bike to the rider's weight.
You could seal all the frame tubes and fill them with heavier or lighter gases as appropriate.
Would tread depth have to be proportionate too?
Yup, and gearing, disc size and caliper ratio.
Seatpost, axle and saddle rail diameter too.
I think I'll just stick with the one I've got.
Interesting GW I don't think I've ever heard of anyone basing their frame choice on the downtube length, most manufacturers don't even seem to publish that number so it must be a right bugger finding frames...
I can get my head around the concept of "Effective Toptube" or "Front Centre" measurements, but really I suppose what you need to look at with bike fit is the bike as a whole assembly fitting the lump sat on top.
I took dimensions for my DH bike a while ago, before tweaking some parts on it I measured everything longitudinally from the rear axle using a plumb bob, I took the Distances to the BB (Effectively the static CS length) and Front axle (Wheelbase) and I took a dimension based on the the end of the Bars (Minus CS length this should give me a good idea of the bikes "Front Centres" I think) along with Static BB Height and HA....
Of course none of these measurements consider suspension sag they're just a static reference for setup purposes.
And I still need to take all the same measurements again, since tweaking the bike it rides much better, I think the Wheelbase will have increased and the front centre will probably be marginally reduced.
I just want to get some reference measurements on paper as a useful future reference and possibly a help for setting up my HT.
As all of these things actuially reference back to choice of frame, well I suppose you need to consider what parts you might fit to any given bike to produce the contact positions/layout you want, CS, TT length, BB height and HA and a few other measurements (Fork A-C) might give an indication of where your bars will end up relative to your cranks and where your wheel axles will be relative to the rest of the bike, and what this means for the bike in use? most of this is focused on handling but what about climbing? yet another set of compromises to manage...
It's almost worth measuring the key dimensions all of my bikes and just drawing them up for my own benefit, I know how they all ride but I don't think I'm unique in not actually knowing all the important figures for my bikes, which when you say it sounds so stupid - there are actually very few bit of sporting equipment which have quite the number of ergonomic adjustments that a bicycle has, but alot of people seem to base their setup on either guess work and doing it by eye...
In fact I should pronbably get some proper measurements for my own body as well, not just height but my limbs - I'm 5' 10" but that means almost bugger all, I could have a stumpy torso and long legs or the complete opposite, my arms could be longer than GWs despite him being a bit taller, we are not all uniformly scaled versions of the same set of basic dimensions, and should not assume so when setting up a bike...
People go to this much effort?
Surely the logical conclusion to all this is that tall blokes on 29ers with long stays are the most Gnarrrrrr as proportionaly they are bigger therfore can ride over bigger rocks.