Frame sizes - dependent on riding type?
butcher of bakersfield
Posts: 1,233
If there's one thing that grates me about my current bike, it's the size of the frame. Whilst it's fine for long journeys, and not overly big on me (the seat's raised a fair bit generally), I have no control over it for anything else.
Many moons ago, I rode BMX. I wasn't particularly good at it, but bunnyhops of 2 feet or so weren't too difficult. Probably couldn't do it now but it wasn't that long ago, I reckon I could pull out a half decent effort still. I've never been able to do anything of the sort on a mountain bike though. My bowels quiver everytime I approach a curb to hop up, knowing that the difference between success and instant tyre deflation can be measured in milimeters. About 50% of the time I won't even attempt it.
Neither can I manual on my current bike. Seat down, arse over the back wheel, and, nope, nothing. Front wheel clears the ground by a few inches and stays there for maybe a full second, if I'm lucky. So drop offs are out unless I'm comfortable that I have enough speed not to drop the front wheel before I'm off the edge. Because, Christ, that's a heart stopping moment.
So, whilst the size of the bike is fine for general riding, does it make sense to ride a bike a couple of inches on the small side when it comes to trails and other technical riding? And if so will I be compromising other types of riding? Will it cure my ailments? Or am I just s**t?
Many moons ago, I rode BMX. I wasn't particularly good at it, but bunnyhops of 2 feet or so weren't too difficult. Probably couldn't do it now but it wasn't that long ago, I reckon I could pull out a half decent effort still. I've never been able to do anything of the sort on a mountain bike though. My bowels quiver everytime I approach a curb to hop up, knowing that the difference between success and instant tyre deflation can be measured in milimeters. About 50% of the time I won't even attempt it.
Neither can I manual on my current bike. Seat down, arse over the back wheel, and, nope, nothing. Front wheel clears the ground by a few inches and stays there for maybe a full second, if I'm lucky. So drop offs are out unless I'm comfortable that I have enough speed not to drop the front wheel before I'm off the edge. Because, Christ, that's a heart stopping moment.
So, whilst the size of the bike is fine for general riding, does it make sense to ride a bike a couple of inches on the small side when it comes to trails and other technical riding? And if so will I be compromising other types of riding? Will it cure my ailments? Or am I just s**t?
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Comments
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so what is your "current" bike?"Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
Parktools :?:SheldonBrown0 -
Old (about '97) GT. Don't know the model. 17".
I'm 5'8", but short legs too.0 -
90s GTs had fairly short top tubes for the size.0
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If you're under 6ft tall, then a 16" hardtail is good for everything.
15" is a bit too low, but if you're not too close to the 6ft, even better.0 -
supersonic wrote:90s GTs had fairly short top tubes for the size.
what were the chainstay lengths like?
Frame "size" has very little to do with anything. how it is put together does."Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
Parktools :?:SheldonBrown0 -
Sounds like your stem is too long and you bars too low. A budget 50mm or shorter stem is a quick, easy and relitively inexpensive way to get it up :roll: I'm 6'2" and have an 18" frame just so I can move about it a bit more, on a road bike I'd need 21" or more.-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
Mongoose Teocali
Giant STP0
Why are MTB economics; spend twice as much as you intended, but only half as much as you wish you could afford? :roll:0 -
nicklouse wrote:supersonic wrote:90s GTs had fairly short top tubes for the size.
what were the chainstay lengths like?
Frame "size" has very little to do with anything. how it is put together does.
What I am saying is, for a listed frame 'size', almost all GTs today have greater standover heights, longer wheelbases and longer top tubes.0 -
Xtreem wrote:If you're under 6ft tall, then a 16" hardtail is good for everything.
15" is a bit too low, but if you're not too close to the 6ft, even better.
But you don't know the other measurements ;-)0 -
I understand that this mostly comes down to frame geometry, but I have no idea what geometry I should be looking for, or what to expect. I mean, am I being realistic in expecting this from a mountain bike? Although I do see people on hardtail trail bikes that seem to handle like BMXs with big wheels. I want that versatility.supersonic wrote:What I am saying is, for a listed frame 'size', almost all GTs today have greater standover heights, longer wheelbases and longer top tubes.
And I have no idea what any of that means. Is that good or bad? In my way of logical thinking, a longer wheelbase/frame suggests less leverage on lifting the front, which appears to be my main issue, unless it has shorter chainstays - possibly the reason for the longer top tube? And I guess BB height would make a difference too?
I'm not sure what I'm meant to be looking for?
Sure, I can try bikes out in the shop, but it's not something easy to ascertain rolling around the shop carpark. I'd like to be backed up with a fair knowledge of frame size, geometry and the differences in riding style they entail.0 -
Not good or bad, just an observation - if you picked up the same 'size' GT today it would feel very different. It highlights how frames from different manufacturers vary, so it is down as usual to what feel best!
Saying that you can make some general comments. More standover height can offer more manoevrabilty and crown jewel clearence, a longer top tube with shorter stem will preserve the reach whilst quickening the steering feel; longer wheelbases and chainstays tend to be more stable, as do slacker head angles. Low BB height lowers the COG and can improve cornering at high speed (but you may gound the pedals easier).
Also consider the bar height, seat post layback, saddle rails, seat angle and distance behind the bottom bracket, downtube length (which is an effective way of comparing the pedal position to where the bars may be, useful for riding when standing - a similar measurement can be got from top tube length and comparing seat angles)
A lot to consider, can be very confusing, one measurement can effect another so the actual feel rather than the maths is often the best indicator!
Personally when sat down I don't like to be too far behind the BB - I find it more efficient this way. So I have a fairly steep seat angle, but long top tube (rather than shorter toptube and slacker head angle which would give me the same reach maybe, but place me further back behind the BB). I have about 4 inches of standover clearance which is enough for me, and a fairly steep head angle which makes for fast steering, if not as stable. Stem at 90mm compliments this, and combined with the top tube length gives me a stretched out position which I prefer for long rides.
My '18 inch' Medium Zaskar Team.0 -
My 17" SS XC bike.
the best way to find out what is right is bum on "leather"."Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
Parktools :?:SheldonBrown0
