So, who’s a mathematician/engineer? My frame ran a 51mm stroke shock for 125mm travel. Now I have a 57mm stroke shock fitted (same length so no other change).

How much travel do I get now?!

FYI It’s a Blur TRC with a DBAir CS. I’ve buzzed off the front derailleur cable stop so there’s no frame contact on bottom out- all good!

Thanks guys

*holds fingers about this > < far apart*

[edit ] forum removes duplicate spaces, d’oh!

11% longer stroke, ~140mm assuming it’s a relatively linear relationship

I thought 140mm. Brilliant! Cheers buddy. No contact with any parts (now the cable stop has gone) so it should make my TRC even better. I don’t anticipate much difference in feel on the trail. Well, difference from the CCDB over the RP23 but not the extra squish.

Cheers!

Easy way to find out what a different length shock would do is

Normal travel 125 ÷ normal stroke 51 = 2.45(leverage ratio)

Then multiply 2.45 by 57 which gives 139.7mm travel

Thanks Transporter- exactly with what my civil’s pal came back with!

Cheers all!

Does it not feel odd with a 20mm (ish) higher bb) and much steeper ha?

http://linkagedesign.blogspot.co.uk/2011/05/santa-cruz-blur-trc-2012.html

Agree you’ll end up with a hair under 140mm.

Just bear in mind the impact on geometry, at your new sag point (assuming you’ll run the same % sag), the bike will be sitting further into the travel, bb will be lower, HA and SA will be slacker, CS will be longer too.

I don’t think it will behave weirdly too assuming tunes between the 2 shocks are identical or very similar.

Does it not feel odd with a 20mm (ish) higher bb) and much steeper ha?

Shock length is same so nothing will change…

My bad 😳

Cheers guys. I don’t think it will handle too differently. I have gone from a RP23 which wasn’t the ideal tune for me (under damped for my weight but came new with the frame) to the ultra adjustable CCDB Air CS. I’ve mounted the shock and cycled it through its travel and cannot see anything dramatic like stupidly low B/B or anything.

I’m hoping it’ll feel similar but more ‘planted’ it’s my do it all ragger that gets a hammering. I think the extra few mm’s squish out back will be a good thing.

Cheers!

Make sure you spend plenty of time getting the shock set up to your liking, just a few clicks of one of the adjustments or a few PSI (or both) can change the feel significantly, it did for my Codeine anyway.

Thanks for the input buddy. I’m going to have to go off the Blur TRC base tunes for a 51mm stroke shock. Obviously it’s a little different for my 57mm! It should be a starting point though.

Cheers

Check nothing is going to bottom out with the new shock stroke!

http://fcdn.mtbr.com/attachments/shocks-suspension/967429d1424880714-vorsprung-corset-chumba01.jpg

So far everyone is suggesting a linear relationship which isn’t accurate for a linkage bike, especially a VPP.

Look at this graph. Wheel travel on the x and leverage ratio on the y. The first thing to note is that a blur had quite an atypical falling rate towards the end of its travel, compared with other bikes. What you ideally need to know is what that graph looks like if you continue the green line out towards the right. You have to extrapolate a fair bit, which is prone to error, but it looks as though the line would continue to plummet – ie the ratio would fall. This means that you’ll be somewhere near a 1:1 ratio so your extra 6mm of shock travel might only buy you 6-10mm of rear wheel travel.

You could always just measure the rear wheel travel.

My other comment would be that although nothing fouls in the garage, by the time you add in some wheel flex / frame flex, you may find that things are rubbing. Just keep an eye on this on the first few miles of riding the thing.

Anyway, enjoy. I always wanted a TRc.

Thanks for the good info buddy.

Nothing fouls- rode it around the streets for a bit today- it feels brilliant. It feels bottomless now, although I believe that’s down to the shock rather than the extra 6mm stroke!

It certainly feels more like a 140mm bike. I don’t have the time to work out the actual travel but I’m happy so it’s job done!

Thanks all.