Fork Replacement Question

jonnystv said:

Dear All

I have a 2005 Gary Fisher Utopia. It is equipped with Rock Shox GPS Metro suspension forks.

As the vast majority of my riding is on the road I would like to replace these with rigid forks.

I have been looking at the offerings from Surly (Karate Monkey) and On One (Superlight Fork).

The bike has 29" wheels & disc brakes.

What I would like to know is if forks that accommodate this size of wheel are standard lengths? If not will shorter or longer forks affect the bike?

Also any fork recommendations would be gratefully received.

Cheers
Jonny

ANY cyclocross fork will work ...

Nashbar currently has a suitable fork on sale for $50 + shipping; so, if you're Stateside, that should work for you ... OR, you could spend more if you really wanted to!

alfeng said:

ANY cyclocross fork will work ...

Nashbar currently has a suitable fork on sale for $50 + shipping; so, if you're Stateside, that should work for you ... OR, you could spend more if you really wanted to!

Well, not really. First of all, a cyclocross fork won't have enough clearance for 29" tires. Secondly, it would be too short resulting in an excessively steep head tube angle. The Surly Karate Monkey fork is corrected for 85mm of suspension travel. I don't know about the axel to crown on the On One.

artmichalek said:

Well, not really. First of all, a cyclocross fork won't have enough clearance for 29" tires. Secondly, it would be too short resulting in an excessively steep head tube angle. The Surly Karate Monkey fork is corrected for 85mm of suspension travel. I don't know about the axel to crown on the On One.

HMmmm. You are absolutely right, technically ... sorry!

While the crown may be far enough away on a CX fork, the shoulders on a CX fork could be too narrow for a 700x58 tire; but, I don't think a 700x58 will fit in that Rock Shox GPS Metro fork, either! Was that the original fork for the bike?

I'm not sure a CX fork is actually too short (dropouts to crown) for non-technical riding ... particularly, if jonnystv does not opt for a 700x58 off-road tires, and continues to only use 700x42 tires -- basically, hybrid tires -- which I believe the Utopia comes-from-the-factory with.

The head tube WILL be about 1º steeper, but, it is probably pretty slack, already and paved riding may benefit.

The bottom bracket height will be lowered, fractionally.

If 700x58 tires will fit in the frame's rear triangle, then the Surly Karate Monkey fork is a better option just so the option of the mega 700x58 tires can remain ... but, I'm so cheap that I'd still go with the readily available cyclocross/touring fork from Nashbar -- you know, penny wise, pound foolish!

Alfeng

Thanks for the reply.

The GPS Metro fork is the one it came with. I'm highly unlikely to be using 700x58 tyres. In fact I recently put on a pair of 700x38 Specialized Crossroads as I'm only ever on hardpack or tarmac.

The cobbled streets of Edinburgh can put a bit of a strain on the backside though!

"The head tube WILL be about 1º steeper, but, it is probably pretty slack, already and paved riding may benefit."

Not being particularly technical, a laymans explanation of the above would be most appreciated.

Jonny

jonnystv said:

Alfeng

Thanks for the reply.

The GPS Metro fork is the one it came with. I'm highly unlikely to be using 700x58 tyres. In fact I recently put on a pair of 700x38 Specialized Crossroads as I'm only ever on hardpack or tarmac.

The cobbled streets of Edinburgh can put a bit of a strain on the backside though!

"The head tube WILL be about 1º steeper, but, it is probably pretty slack, already and paved riding may benefit."

Not being particularly technical, a laymans explanation of the above would be most appreciated.

Jonny

Oh, I can see that you're probably going to get me into some sort of trouble by asking me to clarify something I've said -- but, here goes ...

I think, as a sweeping generalization, it can be suggested that the head tube on a regular, 26" mountain bike is about 71º ... is that right? I presume the seat tube & head tube angles are ABOUT THE SAME for a 29er ...

Making the head tube steeper by a degree or two (that is, as you lower the front end by using a shorter fork, the head tube will be closer to vertical -- 90º), will result in a head tube which is probably going to be between 72º & 73º.

72º is a traditional (whatever THAT means!) angle for touring bikes.

73º is a common angle for fast touring AND most "racing" frames.

The attached picture, FWIW, is a 26" hardtail frame which has a STANDARD 700c ROAD FORK (700x25 maximum tire size) mated to it.

Obviously, NASHBAR is probably not a practical mail order retailer for you, but there must be comparable sources for CX forks in the UK.

Alfeng,

Thanks for the info.

I expect there's some maths I can do to work out the suitability of potential purchases. And yes, there are plenty of suitable component suppliers in the UK.

Am I right in thinking that a slightly steeper angle may make the steering a bit sharper on hard surfaces?

Sorry about all the questions but how else does one learn.

Cheers
Jonny

jonnystv said:

Alfeng,

Thanks for the info.

I expect there's some maths I can do to work out the suitability of potential purchases. And yes, there are plenty of suitable component suppliers in the UK.

Am I right in thinking that a slightly steeper angle may make the steering a bit sharper on hard surfaces?

Sorry about all the questions but how else does one learn.

Cheers
Jonny

If by "sharper" you mean less lugubrious, then "yes" -- it will take less effort to turn the handlebars & front wheel.