Squish squish... (MTB thread)

[I-S]

Ahh, an entertaining evening.

I decided (possibly against better judgement) to strip down and rebuild my Magura Asgard suspension forks. The main reason for this was to change the damping oil from 20wt to 15wt. I'm right at the bottom end of the weight range that they're specced for out of the factory, and I found both the compression and rebound damping to be too slow (even with the rebound dialled right out... there's no compression adjustment on the Asgards).

Taking them apart is good fun. Taking the bolts out of the bottom of the lower legs doesn't seem to unleash the expected torrent of fork oil. You have to take them apart a little further, and of course at that point they pee oil all over the place when you least suspect.

The oil bears an uncanny resemblance to automatic transmission fluid in both look and smell. Not that surprising really, as ATF is used as fork oil rather a lot in motorcycles. MTB forks usually use thinner oils though (even as low as 2.5wt, which is a lot like water).

A quick clean up (not much to clean up... the seals on magura forks are better than any other fork I've ever worked on), and put them back together with the 15wt oil. They appear still to work at least.

Thankfully, this operation seems to have done exactly what I wanted to achieve. The compression damping is softer and the rebound is quicker; too quick actually, but a couple of turns of the rebound adjuster and it was just right. Slightly higher air pressure required now as compared to what was needed with the 20wt, to tune the compression about right. Just need to get it dialled in with some test rides now.

Oh, and it makes louder squishy noises now.

Later this week the bike shop is supposed to be replacing the main pivot bearings in the frame (Marin made the mistake of guaranteeing them for life... This isn't the first single-pivot marin I've seen with play in the main bearings), and with my recent work on the suspension (new float RC, stainless lower bushing (much stiffer), Ti bolt (to counteract the weight of the bushing)) should all result in being well set up for the season's riding. All I need now is a lighter stem.

Squish squish.

 

[julian2002]

how long do you expect the bearings to last? i must admit the extra complexity of them was one of the main reasons i went hardtail. i've not had to worry about faffing with my forks as yet - i'll take the bike back to sjs in the autumn and get them to service the thing (rohloff, brakes and fork) as i'm all thumbs when it comes to that kind of thing and end up with unexpected 'spare' parts. if you know what i mean.

what sort of stem are you looking for - i recently switched to a hope xc stem and would heartily reccomend it - you'd likely be able to get lighter but it'd probably have to be carbon and i'd not trust carbon on such a knock prone item. it also comes in a variety of blingy colours which is also a bonus. next on the shiney bikey list for me are new cranks - i'm thinking middleburn rs8's at the moment but i'm fickle and changeable.

what are your thoughts on bottom brackets? square taper, isis or external bb's? i'm thinking the skf isis 450's at the moment as i'm not convinced that an external bearing bb will work well with my eccentric bb shell.

 

[I-S]

I bought the frame S/H. I think it's because I upgraded the lower shock bush to steel that has stiffened the upper part of the swingarm which has made the play in the lower part more noticeable.

I'll probably go for a Ritchey Comp. I've got one on my SS, and it's lighter than the hope and comes in at around £15. The hope is pretty heavy in the scheme of things. As for breaking stuff.... I'm too light.

BBs... lots of people seem to have issues with ISIS bearings wearing prematurely. Again, I think this is down to rider weight and riding style. My FS has an FSA Platinum ISIS BB and Ritchey Pro V2 cranks. My singlespeed has a shimano UN52 square-taper BB and Grey cranks. Personally, I can't say I notice a difference in their performance.