# Angleset Headset and Bottom Bracket height



## Ottoreni (Jan 27, 2004)

Not a frame building question, but I figured builders would most likely know the answer.

I am planning on getting an angle-set headset, but want to know how will it change my bottom bracket height. 

Is there a rule of thumb? Like a 1 degree angle change (slackening) equals x amount of lowering in the bottom bracket height?


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## pvd (Jan 4, 2006)

Interesting. I should figure that out.

Head Angle Change With Suspension Travel - Pvdwiki

Remember that you can make a bike work worse with an angleset. I've a few bikes that have optimal head angles out of the box. Also, if the bike is already low, it will get noticably lower with the angleset.

I put one on my SC Butcher (160Van). I wanted more of a downhill bias and put in a 0.5 degree cup. I got that. I did get worse up the hill. More importantly, the already perfect BB height got much lower. I've got to ride it a bit more to see if it's a serious problem, but I'm sure most people wouldn't like the bike as low as it is now.

Also, on one of my PVD trail bikes, I tried another 0.5 degree HA with the Angleset. It made the bike feel like garbage. My prior testing had already got the slackest angle into the design that I built the bike with.

I think that most people shouldn't use this type of adjustment as it's far outside their reason. Most folks that could use it are Enduro/Super D racers and DH racers to adjust a bike to a specific course need.


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## ade ward (Jun 23, 2009)

I think the change in front centre would also be very interesting


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## RCP FAB (Jun 15, 2011)

Just quickly.

A frame with a 71* head angle and a 526mm fork has a head tube height (vertical from ground to bottom center of head tube) of 497.34mm

Change the angle to 70* and the head tube height of 494.28 A change of ~3mm.

Assuming the frame has an 1100mm wheel base and 435mm chain stays, that's a ratio of .395:1, meaning the bottom bracket height difference will be 39.5% of the head tube height.

Bottom bracket will drop ~1.2mm, or roughly, nothing you will ever notice.

Front center will increase ~8.6mm

Again, this was just quick, not factoring in fork rake, and what not, but none of the changes are going to be noticeable unless you plan on changing the head angle severely.


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## pvd (Jan 4, 2006)

RCP FAB said:


> but none of the changes are going to be noticeable unless you plan on changing the head angle severely.


Have you tried an AngleSet? A 0.50 degree angle change is extremely noticable.


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## RCP FAB (Jun 15, 2011)

pvd said:


> Have you tried an AngleSet? A 0.50 degree angle change is extremely noticable.


Let me rephrase...

none of the changes *that are effected besides the head tube angle* are going to be noticeable unless you plan on changing the head angle severely. I was mostly referring the the change it BB drop. 2 exact frames, except one has a 1.2mm lower BB, are going to ride the same.


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## pvd (Jan 4, 2006)

You are assuming that your math is right, which I seriously doubt.

I havent done the math yet, but I think I will. Regardless. The change in BB height is very noticable.


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## RCP FAB (Jun 15, 2011)

Just to double check my work. Red is stock, White would be with a 1* angle set.

I dunno, maybe I'm missing something?


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## pvd (Jan 4, 2006)

All I can think is that the Angleset pivot is not correct on your drawing. The pivot is in the upper set, I'm estimating about an inch above the top of the head tube. I'd have to measure to be sure but that's a close enough approximation. Also, the lower cup has the offset (generally), but the degree notation is based on a specific head tube length. I'll have to measure the offset too.

See if that changes things more.


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## pvd (Jan 4, 2006)

Ahhh...

Here we go. I couldn't find it the first time around but it should clear some stuff up.

Cane Creek Cycling Components :: AngleSet Calculator


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## RCP FAB (Jun 15, 2011)

pvd said:


> Ahhh...
> 
> Here we go. I couldn't find it the first time around but it should clear some stuff up.
> 
> Cane Creek Cycling Components :: AngleSet Calculator


Yeah, I dunno man. that link puts up damn near exactly what I got with math and CAD

Angle Change From Stack Height:
-0 °
Angle Change from Offset:
-0.9 °
Total Angle Change:
-0.9 °
New Effective Headtube Angle:
70.1 °
Wheelbase Change:
9.5 mm
New Wheelbase:
1097.5 mm
Change in Bottom Bracket Height:
-1.6 mm
Cockpit Change:
0 mm


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## j-ro (Feb 21, 2009)

How are they ever going to sell angle sets with you two around?


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## Teague (Jul 2, 2005)

I havn't done the math, but i think that there will have more effect on the BB height at slacker head angles. Try it with say 67 degrees slacked out a degree to 66. I could be completely off but i think this is more relevant to most people that are using anglesets anyway.

Teague


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## Feldybikes (Feb 17, 2004)

^^^You're right, the bottom bracket height difference comes from the ratio of the sine of the head angle (among other things), so it makes a bigger difference at lower head angles (assuming anything resembling a normal bike). But I would guess that the difference between 66 and 67 degrees is still <5mm in BB height (depending upon fork length & wheelbase, I'd wager that's not a ton for most people who probably don't even set their preload that precisely.


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## bee (Apr 7, 2008)

Yeah, it is not a linear relationship. Slacker head angle changes have a more pronounced change in BB drop.


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## future9398 (Dec 12, 2012)

i think the seat tube angle will change as well, right?


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