26erv29er: talk to me about headangles

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26erv29er: talk to me about headangles

13 posts & 10 voices | Started 5 months ago by ianpinder | Latest reply from big_n_daft

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ianpinder - Member

For some reason headangles on 29er bikes seem to be a lot steeper then 26ers.

Is this down to trying to make them more manoeuvrable or more to do with most 29er frames at the minute seem to be cross country.

My 26er frame I am replacing had a ha of 67.7 and it was an am bike.

My new 29er coming to replace I have specked a 68.5 degree ha on it, but I'm wondering if it should not be slacker, to around 68, or 67.5.

Opinions please, and no, as it's custom I can not go and demo a few either

Bike is going to be a nicolai helius am/ac mush up with a pinion gearbox

Posted 5 months ago #
clubber - Member

Both to some extent though also that 29ers typically have shorter forks for the same suspension effect.

Posted 5 months ago #
chiefgrooveguru - Member

It's because it's the trail that matters, not the head angle. Increase the wheel diameter and you get more trail for a given head angle.

Posted 5 months ago #
TooTall - Member

67.5 is the angle for a Lenz Lunchbox and that is pretty much the slack end of 29er. My Sultan is 69.5 and is the 29er version of the 5 Spot and does rather well.

You'll be reet.

Posted 5 months ago #
ianpinder - Member

Ok cool, my am 26er bike had 160 mm of travel on the front, so my 29er am bike only has 140mm, however I'll make the headangle the same on both because they are for the same riding

Posted 5 months ago #
clubber - Member

head angle is only one factor to consider - trail, weight distribution, etc all have at least as big a part to play

You really can't use it as a direct comparison between a 29er and a 26" bike...

Posted 5 months ago #
convert - Member

Listen to chiefgrooveguru above - you want the trail of both to be the same and that will require a different headangle. It's all about trigonometry innit!

Posted 5 months ago #
jameso - Member

What fork are you using, ie how much rake does it have?

If you make the HA and fork rake the same, the 29er wil have more trail and feel floppier to steer. Also your 160mm 26" has more room to steepen under full compression and more sag than a 140mm fork,so the 140mm fork will run a tad slacker on average.
I think it's better to have a bit more trail on a 29er rather than a steep HA to compensate for the wheel size, but generally a degree-ish steeper with a longer rake fork is ok - keeps the axle in front of your bars but isn't too floppy to steer. But it's going to feel different whatever you do.

Posted 5 months ago #
Sam - Member

Listen to chiefgrooveguru above - you want the trail of both to be the same and that will require a different headangle
Don't necessarily agree with that - trail is very important, but is still only one ingredient in the bike geometry stew. All else being equal I think you want to have less trail on a 29er than a 26er for the same 'type' of bike due to the gyroscopic effect of the wheel and the impact of the changed contact patch shape on pneumatic trail.

Posted 5 months ago #
Duggie Style - Member

My sultan is running a 140mm fork so HA is about 68.5 and it feels quite steering floppy at low speed, bit like my Spesh Pitch with a 160mm lyrik.

Bike is going to be a nicolai helius am/ac mush up with a pinion gearbox

That there must be a serious bit of wedge

Posted 5 months ago #
ianpinder - Member

Ds-slightly, once you add in custom geometry and ano colour.

Ok

26;

Trail - 100
Ha- 67.7
Fork offset - 37
Chain stay - 431
Total wheelbase - 1169
Tt - 625
St - 430

29;

Trail - 96
Ha- 68.5
Fork offset - 46
Chain stay - 461
Total wheelbase - 1196
Tt - 625
St - 430

Posted 5 months ago #
Rorschach - Member

I'll make the headangle the same on both because they are for the same riding

And when you do the 29er will feel like a barge and then you'll think its the wheels fault and right off 29ers.
Where have you got the idea would you should have the same geometry on 26-29's.This is where they started 10 years ago!!!!

Posted 5 months ago #
big_n_daft - Member

My new 29er coming to replace I have specked a 68.5 degree ha on it, but I'm wondering if it should not be slacker, to around 68, or 67.5.

Opinions please, and no, as it's custom I can not go and demo a few either

personnally I would have copied the best frame you have ridden, making up your own geometry is just a receipe for a expensive gamble

Posted 5 months ago #

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