[Closed] Heavy lads that ride small FS bikes ? Frame blowing through travel

what's the frame and shock ?

Frame size wouldn't really have anything to do with it, but if the stroke length is short relative to the travel then you'll have challenges getting enough pressure in an air can to support your weight, prevent it blowing through the travel and not feel like you're riding a hard tail.

[list]Frames a Titus Motolite 09 model ... 5" travel
shocks a fox rp23
small ML uses a 6.5 X 1.5 shock and and 3.33:1 leverage ratio
Starting to look like i`ll have a small motolite for sale very shortly !

that is quite a leverage ratio.
what pressure is the shock rated to, is the sag set correctly.

nowt to do with the frame size really.

frame size dont matter.
call tftuned for set up adivce

On my Helius I have to put vastly different air pressures in the Float shock, depending on which travel setting it is set. The longer the travel setting the higher the pressure. However, regardless of how much air is in it (about 250psi for the 200mm setting), if I set the sag correctly then the suspension works correctly.

Be aware that some frame/suspension designs don't work that well with high volume shocks - the Fox Dhx 5 having a particularly bad reputation for blowing through the midstroke.

As said above, the frame size has nothing to do with it.

You can improve matters a lot by putting a coil shock on to replace the air can, assuming you can get one in that config.

Shox rated to 300lb .. and it takes all that and still get more sag than id like !

dont want this to sound a silly question, but how much sag would you like?

jedi - Member
frame size dont matter.
call tftuned for set up adivce

SOOBalias - Member
dont want this to sound a silly question, but how much sag would you like?

isnt it something like 25 % ... was still getting more than that at full pressure

 

the leverage ratio means that you are buggered on that frame, it was designed to have a high leverage ratio to optimise it for smaller/lighter riders.

what's the frame and shock? out of interest must have a pretty high leverage ratio to not allow the shock to deal with a 15 stone rider.

damn sorry computer playing silly beggars 😳

richc - Member
the leverage ratio means that you are buggered on that frame, it was designed to have a high leverage ratio to optimise it for smaller/lighter riders.

Thats my thoughts .... looks like my dream frame will be in the classifieds by the weekend then !! ... Total waste of money

Could always lose loads of weight !!! .. but wheres the fun in that ??
Would rather sell the frame to be honest 😀

can't you run it in 4" travel setting- that'll lower the ratio to 2.66 to 1

I am guessing then that the frame has a different stroke length than larger sizes, which would mean that the comments (mine included) about the frame size not being relevant, are wrong.

If you need something small, with adjustable travel, horst link and quality, then Nicolai would be the way to go.

or a five! 😯

vinnyeh - Member
can't you run it in 4" travel setting- that'll lower the ratio to 2.66 to 1

geetee1972 - Member
I am guessing then that the frame has a different stroke length than larger sizes, which would mean that the comments (mine included) about the frame size not being relevant, are wrong.

If you need something small, with adjustable travel, horst link and quality, then Nicolai would be the way to go.

You can improve matters a lot by putting a coil shock on to replace the air can, assuming you can get one in that config.

Not really going to help much. An air shock tends to help bikes that dive through the travel, as a smaller volume air can (not a high volume one) ramps up at the end which would be a benefit here.

The titus motolite 05 I can see on linkage is a bit odd in that it's falling rate to start with (sags a long way), then gets progressive towards the end of the travel. Looks like good candidate for an air shock.

Like I'm going to disagree with Brant Richards.

early Titus'es had 2 shock mount holes one for coil shocks and one for air, to allow the linkage to be tuned for the shock being used.

early Titus'es had 2 shock mount holes one for coil shocks and one for air, to allow the linkage to be tuned for the shock being used.

Never heard of this before, and not sure why it would be necessary- surely you'd just tune the shock appropriately? I thought the two holes were to change the travel (they were on the motolite I had).

Maybe a manitou 4 way air rear shock. got one for sale

This is a bit extreme, but you could get the front shock mounting moved forward to get a longer shock in. Or maybe a new second mounting on the downtube?

I don't know anything about the bike or Titus, are they a friendly company who might be willing to do this (at a cost) for a customer? For resale purposes it would be much better if this was done by the manufacturer.

If the frame is no good for you then sell it and buy one that is suitable! No point trying to bodge it and end up spending even more cash on it. I'm over 14 stone with all my kit but I'm 6ft1 which makes it much easier in terms of bike choice.

Are you sure that the shock is working correctly and doesn't have a fault of some kind?

Just something to consider.....

You could lose some weight? That would be free, and bring other advantages...

Hmm with your weight and that leverage ratio you are going to struggle to get the bike to feel how you like. I am close to 17stone in all my riding kit and struggle sometimes with bikes with a lot less leverage ratio that that.
you have a few options
1. run the bike in the 4" travel option - less travel but better suspension.
2. sell the frame
3. run the shock with max pressure (or a bit over), wait for shock to blow or wear out fast. repair and repeat.
4. get the shock tuned with more compression damping (will spoil small bump response, and make the suspension feel more harsh)
5. talk to Titus Uk importers - they may have some suggestions http://www.titus-bikes.co.uk/

I am with Brant - a coil shock will tend to blow through its travel more, and the spring will need to be a big heavy lump.

Good luck from another heavy lad.

OK i've been thinking about this and I have a few questions:

Air springs are not linear; I think in terms of the equations that govern the actual spring rate as they move through their cycle they are exponential or something. Which is why they are progressive in terms of spring rate, i.e. the spring rate the air damper sees at the start of the stroke is lower than that it sees at the end of the stroke because of the way that air pressure increases faster than volume decreases.

So that means that the heavier you are, the more pronounced the effect of this progressiveness will be.

Which means that a heavier person, relative to a significantly lighter person, will feel that their air can will either be:

a)Too soft in the middle part of the stroke in order for the end stroke to feel about right
or
b) Too harsh at the end of the stroke in order for the middle part of the stroke to feel right.
or even worse
c)In order to get the bike sagging at the right amount (25%-30%) they have so much air in the can that anything from about the first third of the stroke onwards feels very harsh and over sprung.

I am heavy and feel as though this has been a problem in the past that a coil spring has not presented me with, but i am perfectly happy to be re-educated on the physics behind this thinking.

Obviously things will be effected considerably by the leverage curves of the bike and these can be matched to compensate for the way an air spring behaves.

Brant et al, how much of this is correct and if it is, how does running a coil mean that, assuming you have the correct spring rate, the shock 'blows through its travel'?

you have a few options
1. run the bike in the 4" travel option - less travel but better suspension.
2. sell the frame
3. run the shock with max pressure (or a bit over), wait for shock to blow or wear out fast. repair and repeat.
4. get the shock tuned with more compression damping (will spoil small bump response, and make the suspension feel more harsh)
5. talk to Titus Uk importers - they may have some suggestions http://www.titus-bikes.co.uk/

6. LOSE WEIGHT

I've gone from 75-68kg in a few months, it's not that hard. If this is your 'dream bike', is it not worth a bit of effort? You'll be quicker up the hills too and probably enjoy it more! Or would you really rather lose a few hundred quid selling it!?

go for a run or 2 you fat knacker! 😯

if you're heavy avoid frames with high leverage ratios.

sell it! and look at the leverage ratio before buying a replacement.

Ps. you won't get a spring stiff enough for it

I'm no expert on leverage ratio but I have a meta 4 with a float R on back with 250psi in it.

I am 18.5 st with no gear and I have had no issues with the rear suspension at all, in fact it works remarkably well.

I'm 14 stone and did the shim mod on my RP23 XV on my Remedy....it reduces the volume so for the same PSI it becomes firmer. It used to blow through the travel a lot but it's noticeably improved now.
Just a thought. Check MTBR for more details

freeridenick - Member
go for a run or 2 you fat knacker!

I thought someone would say that !!
Had a reply back from Titus today and they suggested i get a High Volume canister fitted to the shock and that should help ?
ive emailed Mojo to see if they can help or not ??
Ive never had any issues like this before on all the other FS frames ive had !

Sorry, who ever gave that advise at Titus does not understand the problem as that will make it worse, higher air volume will cause the shock to go through the travel more easily as there is less 'ramping up'.
The issue is the leverage ratio on the frame in relation to your weight.
Titus have designed the frame for a spectrum of users' below your weight and therefore it will not really ever work that well for you regardless of the compression tune on the shock weather it be air or coil (and finding a coil shock and spring of the correct weight/stiffness that short is unlikely).
In short I'd change the frame for something that will work better for you and you'll derive more enjoyment from riding as it stands the Titus will always be a compromise especially if you have to run it at 4" to get it near to working for the money you could get something really nice.
Also 15 stone isn't that heavy, it's just the way they designed the bike!

At 15 stone I wouldn't be looking at any bikes with a leverage ratio over 2.5:1 personally...

I'm 12 and a bit stone, and my Giant Reign X with 6.7" of travel and a 3:1 leverage ratio and a Fox DHX Air sees me with over 200psi in the main chamber of the shock just to get the correct sag on it... If I were 15 stone it would kind of render the air shock useless as I couldn't pump it hard enough for the weight of the rider.

There are plenty of 5" travel bikes out there with 2" stroke shocks fitted as standard, and even some with 2.25 or 2.5" stroke shocks too!