Ohlins Shock

[VTRDark]

Yes heated was the wrong word opposing views is what I meant. Anyway, I really got those spring rates wrong I got that from the R1 forum where that chart comes from. It just goes to show not to believe everything you read on forums

I have just been on the Racetec site and I can now see where you got those figures from. Interestingly though, If the original shock is 916Ib then that comes up as Ohlins -64 / 160Nm so the original spring should be OK for me according to the Racetec calculator which is around the 16kg mark. I'm not sure whether to trust their calculations or not.

(:-})

[Tweety]

I expect you're wondering Carl what have I started

Not at all. A nice healthy heated technical debate is all good as it means I can learn something from it, have an understanding of the suspension, how it works and interacts with the bike. My challenge will be getting the right static sag and rider sag. Now that really will be interesting to see if I can achieve the desired amounts with what I have. I know the spring is probably a bit to heavy for me and I think I need to go with a 95Nm for my weight, possibly a 105Nm as the 95 may be too soft.

I'm staying in Guildford at the moment and there is a suspension guy down the road, Steve Jordan in Leatherhead that is supposed to be very good. So I think I shall pop down and have a chat with him. Maybe get him to work out and tell me the right weight spring that I need as I will be on the bike and kitted up http://www.stevejordanmotorcycles.co.uk/

(:-})

Not heated at all... We haven't started throwing tools yet...

[Tweety]

Actually, the actual definition of how the springs are rated for a specific weight answers that question... The length is entirely irrelevant to speed of travel... The 150 mm spring will compress the same length at the same speed for the same weight as the 170 mm spring... The only part where the length comes into the equation is the "allowed travel" of the spring... IE, at some point the shorter spring will reach the point where it can't compress further, and go solid, before the longer... But really, that should only happen if you are using a spring that is far outside the range specified for...

What I said in the post above


I don't believe the ratio from Honda, I've had a cable tie around the std shock and it bottoms out, therefore using close to the 60mm, there is a bump stop which may limit some of it, but the tie was buried deep in the bump stop. what this means is there's more than 48mm of travel. that 48mm by the calculation would be the point at which the suspension would lock up, or at least soon after.

Actually, the ratio isn't at all from Honda... They give no such specs... It's calculated out by measuring all parts, and the angles, and I double checked it by measuring the wheel travel vs suspension travel with a loading strap... And granted, you are correct in one way... I calculated it two ways, one using raw data, and one using the claimed suspension travel... The claimed suspension travel is what gets you the 48 mm travel... So yeah, you will use all of the available 56-57 mm when needed really, and probably all the 60 mm of the OEM shock...

BUT! Then you are actually allowing more wheel travel than the spec says the bike should have... Ie, no locking up, it just keeps going until stuff like the wheel and under tray hit... Which is something I do not like them do be able too... Which is why the spring becomes a lot more important, as it controls the travel...

[Tweety]

Double post...

[Tweety]

I have just been on the Racetec site and I can now see where you got those figures from. Interestingly though, If the original shock is 916Ib then that comes up as Ohlins -64 / 160Nm so the original spring should be OK for me according to the Racetec calculator which is around the 16kg mark. I'm not sure whether to trust their calculations or not.

(:-})

Actually, you can disregard every one else's math, and check it yourself...

First, the spring weight is given as Nm/mm... It's only written out as Nm, but it's the amount needed to move the spring one mm... So...

Nm/mm -> Kg/mm you need to divide by gravity constant... Which is 9,8... Kg/mm <-> ls/in ... Ask Google...

Meaning that 916 lb/in equals 16.3578981 Kg/mm and then 160,30740138 Nm/mm... So that part they have gotten correct...

[popkat]

Check your spring is right for you Carl, measure rear sag loaded.. If static sag is 12mm (10-12mm is good for a road bike) then loaded it should be between 30-40mm, If your way out of this range then a different spring will be needed. Important to check sag loaded with all your gear on and in the normal riding position, you'll need a helper to hold the bike.

A. Fully extend suspension and measure from fixed point on tail piece (not a flexi part though) to fixed point on swingarm (wheel nuts good)

B. Let suspension settle down, some say don't bounce but I give it a couple of bounces then let it settle, take the same measurement.

The difference between the two is your sag. (subtract B from A)

[VTRDark]

Markus you have thrown me with the Maths I go a bit Dyslexic when bunches of numbers are thrown at me. But I have now realised that when I was converting the Ib to Nm on google I was using Nm and not Nmm. I shall have to watch out for one.

Checking the Sag and playing around with adjustments is going to be my next step. I have not checked things properly since upgrading my forks and have just set things to what feels good. I'm away from home for the next two weeks but that is going to one of the first things I do once I get some volunteers around to help. I need the practise/learning experience as this is an area I have not stepped into. I have always just played with suspension in the past so it feels good. It sure will be interesting to see if I can get the Standard shock within that range for me. I was going to aim for 30mm Rider Sag which I believe falls between race and road. But if I can get it anywhere between 30 and 40 then all is good. I will also check the Free Sag to see if that falls in at around 5mm.

Thanks Guys.

(:-})

[sirch345]

I expect you're wondering Carl what have I started

Not at all. A nice healthy heated technical debate is all good as it means I can learn something from it, have an understanding of the suspension, how it works and interacts with the bike.

I couldn't agree more, it's surprising what knowledge you can gain from just talking about things,

Chris.

[popkat]

Just contacted the owner of my old firestorm, it has an Ohlins shock that I put on it when it was mine. the numbers on the spring are 1093-64/160 209 (don't know what the 209 means though) This is a 16.30kg/917lb spring (150nm) which is pretty much the same rate as the standard shock spring.

With this shock on my firestorm I won 5 races in two meetings and still hold a race speed record at Lydden. on the road it was really good too, when I rode 2 up I had to up the hydraulic preload a bit and add a couple of clicks of compression to account for the extra weight and it work ok for that, this is how it should be. the spring was as supplied with the shock new.

My Penske has a 950lb (about 17.1kg) spring which I feel is too hard, the guy who serviced it went off the racetec site I think, which states 950lb for my weight, i'm now pretty much convinced this is wrong and Ohlins/Honda are right. Although i'll do a static measurement to find out what range it's in first.

Looked round my garage at my spring selection and have 1 x 600lb/10.70kg.. 2 x 800lb/14.30kg which means might to have to buy another spring

[VTRDark]

I think we can safely say that the Racetec calculations are on the stiff side. After reading through a few different forums there are others that are questioning the accuracy of their calculations too. One guy said that their street calculations would get you close to what it should be for track use. How true that is I don't know. Someone else said that maybe their calculations are just for their own equipment including their Valving.

(:-})

[Tweety]

I think we can safely say that the Racetec calculations are on the stiff side. After reading through a few different forums there are others that are questioning the accuracy of their calculations too. One guy said that their street calculations would get you close to what it should be for track use. How true that is I don't know. Someone else said that maybe their calculations are just for their own equipment including their Valving.

(:-})

I'd say that's probably a fair guess, that their parts match their calculations... Don't you? It's when other people use thier numbers on other parts that things get interesting... But yeah, they are probably more calculated for track, than street...

[8541Hawk]

Just a FYI when I set up my Ohlins (though it is the proper VTR unit) on advice of my suspension guy I ordered a spring one down from what Ohlins recommended and it has worked perfect for me.

Which does kind of falling into what the others have been saying