XC Fork - stick to 80mm or go for 100mm?

Brassknocker

Hi there,
I'm about to replace my tired Fox RL80mm forks on my Stumpjumper HT 04 (disc).
I weigh between 70-75kgs - I like racing about uphill - downhill my wheels remain on the ground!

Typical riding is on the road from Edinburgh to Glentress (locked out), the Black climb (favourite bit!), then head down the red descent, then back on the road.
...also occasional loops out to the hills and maybe a summer holiday trip for a transalps type ride.

I've narrowed down the choice to Rockshox SID race, but not sure if I should stick to the 80 size I currently have, or go for the 100?

will it mess up the geometry? or would I benefit from them being longer/stiffer if 'sunk' down to 90/80mm ?


I've been completely happy with the current 80mm set up, but can I only gain with a 100mm?

Any advice would be appreciated!

stevieboy

If the frame will take it i'd go for a 100mm fork personally

Bikerbaboon

the differance would be minimal TBH if you wanted you could set hte 100mm fork with 20% slack takeing it down to 80mm compaired to a stiffer 80mm fork with a 10% slack sitting at 72mm
its a 8mm effective diferance. thats only a couple headset spacers. but the 20% sag you will feel alot plusher over the small bumps but the 10% will feel more direct. I cant see 8mm upfront killing the geomitry. you pays your money you take your chances.

Hope that helps.

Brassknocker

Cheers for the replies guys,

...just one last question on this:-

...Bikerbaboon, that sounds like good sound advice!
(100mm fork with 20% slack taking it down to 80mm compaired to a stiffer 80mm fork with a 10% slack sitting at 72mm)


...but if I'm down at 20% or 30% sag, will I notice quite an upward bounce when pulling on the bars if I'm climbing up a steep hill? (I ride like a roadie on climbs -hands closer to the stem, down over the front and use my arms to pull)

thanks again!

supersonic

Yes, the fork extension would be more noticable.

Chaka Ping

If you're entirely happy with what you've got, go for the same again!

Brassknocker

Chaka Ping wrote:

If you're entirely happy with what you've got, go for the same again!

..that's a good point, the model I was going to order (SID race 80mm 09) are £377, but I see that Merlin have the fork for a bargain £299 but only in 100mm!

So that's the reason for the question, stick to what I know and get the 80s for 80quid more? or buy the 100s and have 80quid in my pocket?!

supersonic

The sids can be internally reduced to 80mm with a spacer.

streako

You ride from Edinburgh to Glentress?!!

Its doable, but I dont like the traffic on the Peebles road, so we tend to drive down there and so have a good, totally off road ride, without traffic worries.

From Edinburgh I just tend to go out in the Pentlands.


Back to topic, defo go for a 100mm as far as I am concerned. Not only does it give more travel, but I prefer the slightly slacker head angle given by a 100mm as opposed to 80mm.

I have ridden 80mm on a Scott Scale and Giant Anthem, and then changed fork to 100mm and much preferred the new position. If you feel you are then too high at the front you could always remove a headset spacer or even flip the stem to a negative rise.

supersonic

I think the Stumpy is quite steep to start. My Zaskar for instance is quite slack, so need to keep 80mm max.

However we do need to compare crown to axle height if talking about fractions.

streako

By the way, Brassknocker, if you like climbing hills, then I could show you my favourite Pentlands loop, which includes plenty of climbing, even more so than GT black.

PM me if you fancy it sometime.

Brassknocker

thanks for the replies and advice,
I've ordered the SID race 09 100s - will let you know how I get on!


Cheers Streako, I'll hopefully have them fitted intime for a ride on Sat, so will be keen to test them out at Glentress for comparison... but we'll see how I get on with the workbench, hacksaw and the starnut!

Would be good to head out into the Pentlands sometime too! - will PM soon.

Cheers,
Si

Tank-slapper

I've got Rebas on both of my bikes.

The HT uses 80mm. These forks came with 100mm travel but the geometry of the bike went to pot - it felt like I was falling over backwards when going uphill. Adding a spacer to reduce the travel is a 30 minute job though. My Spark has 100mm travel and this suits this bike very well.

Here is a link showing you how to change the travel (but also check the technical bulletins on the Rockshox website):

http://dailyyap.blogspot.com/2007/12/bl ... about.html

marinman1

I would go for 100mm and set them quite stiff, gives you a bit more room if things get really rough

Brassknocker

...enjoyed the sun & snow at Glentress & Innerleithen at the w/e on the new 100mm forks - to be honest - I didn't notice a difference (except for the much smoother ride!)

Glad I went for the 100s (+they were cheaper!) - and the new SIDs seemed just as stiff as my old Fox RLs!

Comparing the crown-axle length - the old and new were pretty much the same anyway!

First time I've used Merlincycles too! - delivered in about 24hours! Impressed!!

Thanks for all the help!

mtb1975

Merlin cycles are the best online bike retailer i've ever used, glad the SIDs are working for you, I think people get too hung up on long travel forks, especially for XC duties.

Northwind

streako wrote:

By the way, Brassknocker, if you like climbing hills, then I could show you my favourite Pentlands loop, which includes plenty of climbing

As far as I can tell the Pentlands only go up Where's your loop?

97wilewa01

I just bought a 100mm Reba, the Sid's wee bro, but it is amazing!!! Would be a great choice if the bike can take it...

jason23

streako wrote:

By the way, Brassknocker, if you like climbing hills, then I could show you my favourite Pentlands loop, which includes plenty of climbing, even more so than GT black.

PM me if you fancy it sometime.

Hello Steako,
This Pentlands loop sounds interesting.
So where do you start and finish?

Thanks
J

jason23

streako wrote:

By the way, Brassknocker, if you like climbing hills, then I could show you my favourite Pentlands loop, which includes plenty of climbing, even more so than GT black.

PM me if you fancy it sometime.

Hello Steako,
This Pentlands loop sounds interesting.
So where do you start and finish?

Thanks
J