Bar height and head tube length
Don’t think it’s that simple- there’s a minimum length just for strength and function, and smaller sizes tend to aim for that. But no real reason to go up proportionally, because that takes away options- owners can always add stack height or riser bars but they can’t take away headtube. So steerers tend to go up as the designer desires rather than for riding position I think.
Or put it another way, head tube can only define a minimum practical height, it doesn’t have anything else to do with the actual heightPosted 3 years agoroverpigSubscriber
Most advice I’ve read on finding the optimum height for the bars on a mountain bike relates the height of the bars to the height of the saddle, suggesting that this relationship should be roughly the same for all riders. However, looking at the geometry charts it seems that the head tube never increases in length as fast as the seat tube, suggesting that bike designers expect the bars to be lower relative to the saddle on larger frames.
So, whose right?Posted 3 years agoMrOvershootSubscriber
I think I know what roverpig is getting at, at 6’3″ I’m one of the taller people of a group I ride with and often notice how high relative to the saddle my shorter mates bars are with very few spacers.
Yet only 1 of my bikes has the bars even level with the saddle, this is using an almost ugly amount of spacers and hi-rise bars!
I often feel very pitched over the front downhill, probably why I get the fear down steep stuff as I have had a fair few OTB caused by what to me feels like all my weight being past the front axle.Posted 3 years agodangeourbrainSubscriber
I’m also a taller rider (6’4″ ish) and find that there is a huge discrepancy between my bar and saddle height, I end up riding in something akin to a roadie aero position as my saddle invariably is about 4″ higher than my bars. It doesn’t feel as though the issue is the head tube length though but rather fork length.
It’s doubtless all in my head but no matter how high I set the bars the front of the bike feels very low, on the other hand, stick a longer fork in and it feels much better,though the angles go to pot.
The difference I think is that a longer headtube/more spacers etc results in a shorter effective top tube as the ht and seat tube angles aren’t the same. A longer fork maintains the eftt though.Posted 3 years agoroverpigSubscriber
Head tube increases with frame size on most of the frames
It does, but not by as much as the seat tube. For example, the difference in seat tube length between a medium and a large may be 4cm but the difference in head tube length only 1cm. So, either the larger rider has to use ~3cm more spacers or have their bars ~3cm lower relative to the saddle.
Northwind is right to point out that head tube length only really limits how low you can go though and maybe it is nothing more than trying to give as much room for adjustment as possible while maintaining sufficient strength. I just naively thought that bike designers were working with some sort of model of an average rider and wondered why that model had the bars lower relative to the saddle for the larger rider when that’s not the advice you tend to see.Posted 3 years agodangeourbrainSubscriber
Bear in mind of course that a bike designed (as I’m sure they all are) around Joe average at 5’9″ on a 17.5 frame with 26″ wheels would scale almost exactly to a 19.5″ frame with 29″ wheels… The issue would be horrible bb height amongst other things though.Posted 3 years ago
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