Spring Weight?

[jeffgothro]

I may have a small problem, not sure if this is normal or not - I noticed when I first go on a ride my rear GDT is ok, it seems to support my weight 150-160lbs, but after about an hour of riding it starts to sag - its like already half compressed when I sit on the bike. I also noticed the rear spring says 300 on it and the front says 250 - what gives?

[Colin]

Depends upon which spring rate chart you look at:

But from the Huge spring rate chart for a strut bike, a 300 should be fine for you, if anything a little too strong.
Rider Weight     Spring Rate
up to 140           200
130-170             250
160-200             300
190-230             350
230 +                400

Maybe the spring is a bit "tired" and so underrated? That might explain the gradual sagging, I think you need a new spring.

There's a later ('98) spring rate chart that shows frame outlines and rider weights and this disagrees with the above and says
a 300lb spring is right for a rider of 120 to 160Lb so you're pushing the top end of that and so a 350 would be better which covers rider weights of 150-190lb (bear in mind if you're weighing yourself without riding kit on, that can add quite a few pounds, plus drinks bottles etc....
WORLD CUP
Rider weight in pounds Rider weight in kilogram  Spring rate
90-130    40-60   250in/lbs
120-160  55-75   300in/lbs
150-190  70-85   350in/lbs
180-220  80-100  400in/lbs
210-250  95-115  450in/lbs

I think the "Huge" chart is more accurate and works for me. (200lb weight, 350lb Spring)

You can try winding down the pre-load to reduce the initial sag which should be about 10mm on the shock
But that's a bodge if taken to extremes, so really you need a proper value spring.

It's correct that the front and rear springs are not the same values, different leverage ratios etc...

a 250 on the front is way too high for you, see below, you should have a 200lb spring on there, but you don't mention how that performs.
Girvin Cross-Link:
Rider Weight     Spring Rate
up to 140 175
130-170    200
160-200    200
190-230    225
over 230   250


Hope this all helps

Col.

[jeffgothro]

It does help, actually I like the front the way it is, do you or anyone else know where I can score a spring from?

[Happy Valley]

Concomitant question:

Is there any way to determine spring weight if the labeling is worn off?

Color or ?

Shock in question is NR4 with black spring.

[Colin]

No, if the markings have worn off, you can't visually identify them, all weights came in many colours, usually Red. Black or Yellow. Front springs are generally of a thinner wire diameter than rears.
All you can do is try it and see!

To source a replacement spring you need the following info, free length, inner and outer diameter and then you obviously need the know the lb's per inch compression rate. But also you need to know the stroke of the shock and buy a spring who's coils will not bind (touch) before the stroke bottoms out. e.g. Noleen's are often called NB175-xxx which means that it is a 1 3/4" stroke spring, others are NB2 which means 2"

I don't know the stroke on a GDT, but an ODS is about 1.75" on the front and about 2" on the rear,

A quick search on the web throws up a few options:

e.g. Chain Reaction in the UK
Manitou Shock Spring - Steel
2" x 350 Lbs (For 190/200mm Shock)
RRP £24.99

but check those physical dimensions before you buy!

Col.

[jeffgothro]

Sorry, you lost me, I'm not to good at math and I dont know all that tech'y stuff.

Are you saying I need this?

http://www.chainreactioncycles.com/Models.aspx?ModelID=15335

[rapiddescent]

what's the measurement of the GDT spring?  will a cor spring fit in its place?

callum
rds

[shovelon]

No, this one.

P.N. 65199, In Stock 2" x 350 Lbs (For 190/200mm Shock) £24.99 
 
 

[jeffgothro]

I think you mean this one, I'm on a 300 now and my bike sags big time.



Manitou Shock Spring - Steel
2" x 450 Lbs (For 190/200mm Shock)

65201

Order Total:       $82.70

Sure is alot of money for such a small hunk of metal.

[shovelon]

Nope, 450 lb spring is more suitable for an EVO. I use a 425 on my Oz, and it has much more leverage than your 856.

Now I hate to get personal, but are you a Clydesdale? No really, how much do you pack?

Terry

P.S.  REI can special order manitou and Fox springs for some $35.

[jeffgothro]

I weigh 150-160 and my rear sags after about an hour of riding - I do prefer stiff suspention though, my old proflex the elastomers got so hard it was almost like riding a hard tail, but I really liked it actually, thats why I think I would like 400-450's

P.S.  REI can special order manitou and Fox springs for some $35.

Very cool, I really dont want to spend 80$ for a spring, as of I will end up replacing the front one too with the same color just so they match.

[Colin]

JeffGoThro, (Jeff?)

Trust me on this......(when did you last hear that? <GRIN>)
...........You do not need a 400/450lb spring unless you don't want the rear to move at all!
Either that 300 is faulty or it's not a 300!

I've looked at the photo of your 856 that you've posted, (Nice!)
a) are you sure that's a 300 you have on the rear? The coil wire thickness looks a bit thin for a rear coil, more like a front, are you sure you're not misreading it and it's actually a 200 (i.e. a front coil)?

b) If it really is a 300, then maybe it's just knackered from being used by someone too heavy and you need to replace it.
That may potentially explain the gradual sag over time rather than it just being a lower rated coil that I would expect to sag immediately.
Trust that "Huge spring chart", does anyone else disagree with it? As I say, I run a 350 on the rear and that is pretty stiff for my 200lb weight.

Finally, sorry if I baffled you with the spring selection info, not my intention, I just didn't want to give you only part of the story!

Unfortunately, I don't know of anyone (except Callum - RDS) who you can go to and say, "give me a spare spring for my PRO~FLEX" and Callum does springs for ODS shocks, but maybe they'll fit a GDT, anyone tried this?

So you absolutely have to know the basic sizes of what you need to buy, I can't definitely tell you 'cos I haven't got a GDT to measure.

I'd recommend that you remove the shock from the frame and check it over. remove the spring and definitely check it's marked as a 300, check the compression and rebound of the GDT (but that shouldn't affect sag) just to make sure it's OK.

Then measure the coil:
End to end Length
Outside diameter
Inside diameter

Then you need to look for one that matches that closely, you may have a bit of flexibility on the length depending on how much the pre-load collar winds in and out on the GDT body. A lot of coils do not say these dimensions 'cos they're intended for specific shocks only, so you just need to keep digging.

At the end of the day if you want to go for a 400/450 then that's your choice, but it does seem a waste to drag around the extra weight of a full susser that doesn't bounce! <GRIN>

Col.

[The Mont]

JeffGoThro, (Jeff?)
Unfortunately, I don't know of anyone (except Callum - RDS) who you can go to and say, "give me a spare spring for my PRO~FLEX" and Callum does springs for ODS shocks, but maybe they'll fit a GDT, anyone tried this?

So you absolutely have to know the basic sizes of what you need to buy, I can't definitely tell you 'cos I haven't got a GDT to measure.

I'd recommend that you remove the shock from the frame and check it over. remove the spring and definitely check it's marked as a 300, check the compression and rebound of the GDT (but that shouldn't affect sag) just to make sure it's OK.

Then measure the coil:
End to end Length
Outside diameter
Inside diameter

Then you need to look for one that matches that closely, you may have a bit of flexibility on the length depending on how much the pre-load collar winds in and out on the GDT body. A lot of coils do not say these dimensions 'cos they're intended for specific shocks only, so you just need to keep digging.

At the end of the day if you want to go for a 400/450 then that's your choice, but it does seem a waste to drag around the extra weight of a full susser that doesn't bounce! <GRIN>

Col.

Jeff
I changed my rear GDT for an ODS some time ago and the spring was a straight swap.
My bike came fitted with the yellow springs from new, the front is 250 and the rear 300,
They are both the same length but the rear has a very slightly beefier spring.
I weight about 150lb to 160lb and I've ridden the bike kitted up with a 40lb back pack and all gear on with no problems of excess sagging.
Both my springs are 102mm long aprox 45mm outside diameter, front has 1/2 coil MORE than the rear and is maybee 1/2mm thinner spring diameter
Hope this helps

Monty

[jeffgothro]

Yes, I can most definatly say 100% without a doubt the spring says "300" on it, I would take a pic but my camera blurs from that close up - ok guys, I'm not going to argue, if you say I need a 300 then I guess I need a 300, I just dont the thing sagging on me after riding it around for an hour or so.

[shovelon]

Yes, I can most definatly say 100% without a doubt the spring says "300" on it, I would take a pic but my camera blurs from that close up - ok guys, I'm not going to argue, if you say I need a 300 then I guess I need a 300, I just dont the thing sagging on me after riding it around for an hour or so.

That is just too weird that it sags after an hour, then returns to normal, only to sag again. Me thinks you have a wacky spring?