How to slacken my head angle?

PB Forum :: Mechanics' Lounge
How to slacken my head angle?
Previous Page | Next Page
Author Message
Posted: Mar 19, 2010 at 16:46 Quote
I recently purchased the new Sette Flite 6" frame, and its sweet. The problem is that I am using a Rockshox Revelation fork with 150mm of travel, and its crown to axle height is over 20mm shorter than the Rockshox Domain that comes on the bike. This bike has a 70 degree angle with the domain, so now my bike has something like a 72, causing it to feel twitchy. Any inexpensive ways to put a spacer below by head tube. I have tried using washers to raise it up, but the crown race has to fit snugly on the TAPERED fork steerer tube. So I uses metallic tape wrapped around the tube, but still I get play. I need a professional upgrade that will raise my head tube or somehow slacken my head angle. In the event that this isn't possible or is expensive, are there other ways to make the twitchiness go away or at least reduce it?

Posted: Mar 20, 2010 at 14:56 Quote
if you install a longer stem, this will effectively slacken your head angle - even a stem 20mm longer will make a big difference!!


the reason for this, is that a longer stem provides slower *steering* response, as compared to a shorter stem

it basically takes more effort to turn your bars using the longer stem

the other "fix" is to run a wider handlebar, this will have the same effect as a longer stem!

both a longer stem, or wider handlebar, are both longer "levers" and therefore take more force to rotate for the same rotation angle, as compared to shorter stems or narrower bars

this is a great geometry fix for a "nervous" bike, without wasting money...

have a read of this blog, it will explain...

http://www.freeborn.co.uk/blog/2010/02/20/big-bars-trend-or-truth/

Posted: Mar 20, 2010 at 15:29 Quote
A longer stem will make the bars turn like a bus steering wheel due to the offset from the centre of rotation. Making the bike feel crap. It also compromises the rider position on top of this.

Wide bars are a good idea, but they're still no substitute for a correct fork rake and angle. As you're still not changing the angle the fork is aimed and the bike will still feel twitchy. Just with wider bars

There is no substitute for correct geometry, as I have found with the 67 degree H/A on my Reign X. Luckily for me a angled headset is in the works from a company here.

However, OP you are also lucky.

Cane Creek designed a headset, the XX. Which is designed to allow a 1.5 to 1.125 tapered steerer fork to be used in a 1.125 zero stack headtube. To do this the lower cup houses the bearings externally like a traditional press fit headset, which adds 16mm of below headtube stack height. Similar to adding 16mm of travel (or more accurately Axle to Crown height). on your fork.

This will then make it necessary for you to use a 1.125 to 1.5 adapter crown race.

I'm unsure whether Cane Creek makes the above mentioned crown race, though. So it will be up to you or whoever calls their distributor to get this if it is available.

If not FSA make an adapter Crown race to go with their Extreme Pro 1.5 R headset that is available as a spare. Compatibility wise there may again be a problem if the bearing chamfer is different between FSA and Cane Creek. In that case meaning you would need to find a similar offering to the Cane Creek XX headset from the FSA range of headsets.

My computer would rather not work at the moment so I can't help a great amount.

Posted: Mar 21, 2010 at 6:57 Quote
A longer stem will make the bars turn like a bus steering wheel due to the offset from the centre of rotation. Making the bike feel crap. It also compromises the rider position on top of this.

going from a 50mm to a 70mm will not make the bars turn like a bus steering wheel Wink


its a subtle adjustment that may benefit the rider if their bike feels nervous...and something that can tried in a minute to see the effect, without having to remove and press headsets

it will shift the weight balance into the middle of the bike, but many 6 x 6 bikes are ridden with 70mm stems as it allows a good climbing position, is nimble enough for technical descending and will also load enough weight on the front tire for traction at higher speeds

50mm is unusually short for an all mountain bike

Posted: Mar 21, 2010 at 13:12 Quote
I found a "headset externalizer" online at http://www.enduroforkseals.com/id183.html. It serves as the bottom cup for an internal headset, but places the bearings outside and below the head tube, adding 15 mm of space. It comes with compatible bearings and crown race, all for 50 bucks. I guess that's as cheap as I can get. We do have some longer stems in the garage, I'll consider that. The thing is that this is a 18" frame, a little big for me because I want to use it for years as I grow, but I can move the seat forward more if the longer stem necessitates it.

Posted: Mar 22, 2010 at 15:33 Quote
Maybe this could be the proper way to do it if your head tube has one of the available length and sizes...

http://www.k9industries.com/K9/Reducer.html

Hope this helps. Cheers.

Posted: Mar 24, 2010 at 11:43 Quote
Yeah I looked at K9, the problem is that that thing is really expensive to buy and to ship when converted to U.S. dollars but thanks for the advice.

Posted: Mar 24, 2010 at 18:22 Quote
that's a tough call, I would't go with a longer stem, 20mm really isn't that far.... if you're running, but 20mm in the cockpit can make a huge difference. you could run slightly more sag in the back to help though.

Posted: Sep 3, 2010 at 12:42 Quote
[Quote="hampsteadbandit"]if you install a longer stem, this will effectively slacken your head angle - even a stem 20mm longer will make a big difference!!


the reason for this, is that a longer stem provides slower *steering* response, as compared to a shorter stem. it basically takes more effort to turn your bars using the longer stem
the other "fix" is to run a wider handlebar, this will have the same effect as a longer stem!
both a longer stem, or wider handlebar, are both longer "levers" and therefore take more force to rotate for the same rotation angle, as compared to shorter stems or narrower bars
this is a great geometry fix for a "nervous" bike, without wasting money...

Ok, this is the wrong fix for the underlying issue...
Yes, the head angle is a bit too steep and longer bars and stem will help with the twitchy feel of the front end however; the symptom of having a twitch front end is one of manny that comes with a lower axle top crown height and a steeper head angle. Additional problems over tha actual wheels handeling performance at high speeds, how well the riders weight shifts rearward when goind down a steep shoot and the overall ridability of the bike are others to consider.
You need to understand that fixing a symptom does not neccessarily fix the underlying problem...
Not much you can do to actually fix this problem.... You can experiment with a 24 inch rear wheel, but that will have poor up hill and rock garden performance and will cost a bunch as well...

Best bet is the K9 solution if it fits your steerer length.

Previous Page | Next Page

 
Your subscriptions
no posts

Copyright © 2000 - 2014. Pinkbike.com. All rights reserved.
dv16 0.015463
Mobile Version of Website