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bike handling question about headtube angle and fork offset

Hello, I just signed-up for this site and look forward to meeting likeminded people that share a passion for CX!

I have a question about how head tube rake and fork offset affect handling. I’ll try to keep this as short as possible. I’ve listed my bike build at the bottom.

 

Questions:

How does frame Headtube angle and fork offset relate to each other in terms of handling?

Which fork might be better choice and should I get one with more or less offset?

What other issues could cause my problem? 

Could saddle position w/ a zero set back post cause such an extreme handling characteristic?

Should I move my saddle forward or back to improve the situation? Right now I’m pretty much in the middle.

 

Background:

Last winter I purchased a used Yeti ARC-X custom built for a Yeti employee based on his measurements. I’m not exactly sure how the geometry differs compared to a stock Yeti frame but apparently it is made for someone with a shorter legs and a longer torso. My inseam based on the book between the legs method is 29 inchs which is very short considering I’m 5’ 10. I love the bike, how it looks, rides, without the annoying wheel foot cross over common on smaller frames.

 

The handling issue I have is that bike never feels stable, especially at slower speeds. it always feels like the handle bar/wheel  wants to turn more than I want and I’m constantly fighting to make the bike go straight. The frame has a very slack head tube angle, lots of rake, which I think combined with the Easton EC90X Fork causes the odd handling. The front of the bike also seems to have a tendency to wash out in certain types of turns but usually see it coming so I’m able to catch it but I’m not sure if this is related.

The bike is built up very similar to the factory YETI parts including the Easton EC90-X fork. I raced the bike about 15 times and enjoy it very much but  I’m thinking I might change the fork to a unit with either more or less offset but I don’t really understand how Headtube angle, rake and fork offset together affect handling.


Build List:

Frame - Yeti ARC-X

Fork -Easton EC90-X fork

Stem - Ritchey WCS Logic II 90mm  (white)

Handlebar- Ritchey WCS Logic II 44cm (white)

Seatpost- Thompson elite zero setback

Saddle -Ritchey comp

Shifter/brake lever -Sram Rival

Rear derailuer- Sram Rival

Crank arm -Sram Rival

Chain ring- Single Salsa 38t non ramped chain ring with Paul chain keeper

Cassette- 10 speed 11-26 with deleted 12t

Chain- KMC DX10SC

Headset- Cane Creek s-3

Pedals -Egg beater 2ti

Wheels- Mavic Aksium Race

Tires -Michelin Mud II & Jet

Brakes -Avid Shorty 4

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Replies to This Discussion

ok so I did some research and it seems if I change the fork out for one with more rake, basically any cx fork other then the ec90x which only has 45mm rake vs 47mm for almost all the other options, would likely make the issue worse. does that sound right?

so more rake = faster handling and less rake= more stable? to me that sounds reversed. can someone chime im?

 

an adjustable headset is another option

http://www.universalcycles.com/shopping/product_details.php?id=3785...

 

anyone use one of these before? would I be able to even feel a 1 degree change?

Hey welcome to the Forum,

       Do you know what the head tube angle is?

This may sound like a funny question, but does the front end feel twitchy, or does it feel floppy? 

If the headtube angle is indeed slack, then you are correct, getting a fork with MORE rake, will exaggerate the floppy feeling of the front end.

To define floppy and twitchy.  Twitchy would be if you have a hard time keeping the front wheel straight, but it moves quickly and lightly.

Floppy would be if it's difficult to keep the wheel straight but the front wheel feel heavy.  It's flops to the side.

 

If... you determine that.... an angleset is an option.  Cane creek makes one.

Or, you can contact a local from builder and have them build a nice steel fork that will correct the issue.

Circle A is an option.  They build forks for $175-$200.

 

Lastly.  What's up with the 11-26 cassette missing the 12t cog?

interesting thanks for the reply.  its twitchy for sure, not floppy. I'm not sure how to measure the HT angle but I could take a picture , print it and draw lines and find my protractor that I've not seen in 15 years.

 

 yeah I deleted the 12t and added a 26t. I did this partly for fun, I had never messed with gearing, and partly because I wanted a billy goat gear for hills and 26 is pretty much the largest I could use with a short cage derailleur. might be faster to run but dismounting on steep hill can be awkward and I hate running so I like having the 26t. even with a little 38t up front i've not an issue with top speed and im able to ride over what other cant.

the 90mm stem seems to be the culprit for this cross bike, some bikes arent designed to have a short stem length.  a 110 with short reach bars (70mm-90mm) will give the bike a completely new feeling of stability

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