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Air suspension and large people

19 posts & 11 voices | Started 7 months ago by joolsburger | Latest reply from honourablegeorge

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Fat Boy Springs

joolsburger - Member

Is there any way of setting up airshocks so they actually work as designed for bigger people. Basically I have to have mine at such a pressure fore and aft that small bump compliance means nothing to me. Also at speed with my weight over the front the back end gets skittish.

Is it worth having the shock tuned or is it good money after bad and should I just go coil.

I run my shock at around 200PSI to get the right sag by the way!

Single pivot bike.

Forks are less of an issue they seem to work well.

Posted 7 months ago #
TuckerUK - Member

If forks are anything to go by, air doesn't cut is for us (cough) big-boned riders. I was having to add so much air to get anything like sensible sag that I couldn't then use anywhere near full travel and the fork was very notchy. Converted to coil both legs and no air at all, completely changed the fork, very plush, and full travel with correct sag.

Posted 7 months ago #
thisisnotaspoon - Member

Depends on the fork IMO

At 15stone my maguras suck donkey balls but were brillinat when I was 13stone.

Rock shox sektors with the solo air cartridge (basicly the dual air, with no -ve air valve and a bleed between the two chambers) on the other hand are great.

Posted 7 months ago #
clubber - Member

I'd have said that air suits us big lads very well - no need to buy massive springs, stiction is relatively less (at least that's what I reckon and it's backed up by air forks being crap for sensitivity on really light riders) so TBH I don't have a clue what you're on about. Sounds to me more like your damping maybe isn't set up to suit your weight.

Posted 7 months ago #
honourablegeorge - Member

+1 for Clubber, can do without the hassle of huge, heavy coil springs, never had problems with air stuff.

Posted 7 months ago #
joolsburger - Member

Posted 7 months ago #
Janesy - Member

Plus is not not cheaper and easier to lose weight than spends £100's on new suspension?

Posted 7 months ago #
joolsburger - Member

Think I'll just phone loco

Posted 7 months ago #
z1ppy - Member

Does the shock have a large volume air can? I know that a low volume air can is recommended for the fox shocks on the single pivot C'dale Prophet.

Though it depends on what you consider to be heavy weight, I'm always plesantly surprised to find myself a mid sized @15-16stone compared with many who admit being of a larger nature on here...

Posted 7 months ago #
toys19 - Member

Yeah on my covert it came with a high volume can, so basically the compression ratio is low, bad news for 90kg types like me. I had the rp23 at 240psi to get the right sag, it felt rough on small bumps and then blew through the travel on anything bigger. I got the low volume can (about 20 quid from mojo) and now run about 175psi pressure to get the right sag, feels better over small stuff and doesn't hit full travel unless I do a drop. Happy days.

Posted 7 months ago #
clubber - Member

Ah, so you're talking about the springs being too linear, necessitating high pressure to avoid excessive sag or blowing through the travel...

An easy way to 'fix' that is to add oil to the air chamber - it takes up volume (effectively making it a smaller chamber) so making the spring more progressive/less linear.

Posted 7 months ago #
joolsburger - Member

How much oil? 10ml, 20?? Worth a shot I suppose. I'd expect the compression damping is set up for a nominal pressure in the can not the 180PSI + a bigger person would use.

Posted 7 months ago #
retro83 - Member

joolsburger - Member

How much oil? 10ml, 20?? Worth a shot I suppose. I'd expect the compression damping is set up for a nominal pressure in the can not the 180PSI + a bigger person would use.

Careful putting oil in an air rear shock, at least in Fox ones I've been told it'll migrate to the negative chamber.

If you have a high volume can, you can pack it out with thick grease or fill it with a chunk of plastic cut from one of those CD binders (see here: http://forums.mtbr.com/turner/dw-5-spot-rp23-mod-503070.html - think you need to register to see the pics)

Posted 7 months ago #
honourablegeorge - Member

Covert uses a fairly short shock with a high leverage ratio too, which won't help - Only 50mm shock stroke for 150mm travel.

Posted 7 months ago #
morgs - Member

I'm a very big lad on Magura Menja's and they are lovely!!!

The float on the back doesn't seem to like me though

Posted 7 months ago #
glenh - Member

Careful putting oil in an air rear shock, at least in Fox ones I've been told it'll migrate to the negative chamber.

There needs to be oil in the air chamber to lubricate the seals.
I certainly don't worry about adding a 'generous' amount when servicing the air can on my bike with a falling rate linkage.

Oh, and the negative chamber needs oil too, and on a fox shock at least is joined to the main chamber when the shock is fully extended (that's how it 'auto balances').

I suppose if your shock is in a 'shaft down' position, so the negative chamber is lower than the main chamber, then if you have too much oil in there you risk filling up the negative chamber rather than the positive one, resulting in nasty top out.

Posted 7 months ago #
z1ppy - Member

Highly technical fix for high volume air can's I just spotted...

Posted 7 months ago #
toys19 - Member

h, so you're talking about the springs being too linear, necessitating high pressure to avoid excessive sag or blowing through the travel...

Air is a naturally non linear spring, I think the idea of high volume was to take the "sting" out of the tail of near full compression - probably better for seals and shock life, and probably more plush for light people but a pain for the bigger boned amongst us. I'm on a major weight loss plan and when I get down to 70 kg from 90 kg then I'll be putting the high volume can back on.

Whilst I'm dreaming I'd like a Harrier Jump Jet too..

Posted 7 months ago #
honourablegeorge - Member

Less involved fix:

http://www.mojo.co.uk/airspacers.html

http://www.mojostore.co.uk/acatalog/Air_Spring_Volume_Tuning_Kit.html

Posted 7 months ago #

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