30 replies to this topic

[SteveA]

As you may know I have the Sachs suspension kit supplied by TMS. They run progressive springs which on the road are great but on track are a little bit too soft. I decided to look into buying stiffer linear ones to sort this out. Speaking to Chris at Hofmanns he said he would like to see damper velocity graphs and current spring rates before he could make any suggestions. I spent about 2 weeks contacting various people and trawling the web for information and basically found a velocity graph with no figures on it and nothing else. Sachs got back to me saying that they don't publish this data for their one way dampers. Not happy with this I contacted Pete at Nitron and asked him if they could dyno my shocks and springs, the answer was yes (at a very reasonable cost). I sent them away and now have the velocity graphs and spring rate information. Sachs use a 2" id spring which is very progressive, beginning at 110F & 280R and going up to 425F & 525R (similar to Nitron springs at full compression). Nitron can also supply their springs for my shocks but they need collets as Nitron springs are 2.25" ID. The dampers have a 2:1 ratio rebound to bump, Pete informs me that the std 1 way nitrons are closer to 4:1. Sachs springs are 30% stiffer on the rear and Nitrons are similar at 26%. Will post up graphs and results soon.

Edited by SteveA, 01 June 2009 - 10:15 AM.

[SteveA]

Looking at the graphs i've finally decided (with help and advice from Nitron) to go for the standard Nitron Rates for VXT (375F & 475R) This is the same as it was at 90% compression on the progressive springs. I was always happy with the std springs when pushed hard but didn't like the original roll induced when cornering lightly. These linear springs should sort that out

[theolodian]

Looking at the graphs i've finally decided (with help and advice from Nitron) to go for the standard Nitron Rates for VXT (375F & 475R) This is the same as it was at 90% compression on the progressive springs. I was always happy with the std springs when pushed hard but didn't like the original roll induced when cornering lightly. These linear springs should sort that out

Sounds good. That was a HUGE spread on the progressive rates!

[cnrandall]

I would be interested to see the graphs if you get the chance to post them. Those are VERY soft springs for a VX, I wouldn't even recommend them for the road. For track use on 48's I'm finding the ideal rates on the Europa are 600/850 and for a VX on the road I would suggest a 450/600. Also, one point to note... be careful what you read into the difference in bump/rebound ratio, you don't want to end up using silly rebound levels to control roll, this is the springs job.

[2GOOD]

Sorry totally off topic but, Mr Randall sir, what's happening with your Europa, read your build blog, watched you win at Silverstone & saw the pictures from Brands. Is it going to fight another day?

[cnrandall]

Sorry totally off topic but,

Mr Randall sir, what's happening with your Europa, read your build blog, watched you win at Silverstone & saw the pictures from Brands. Is it going to fight another day?

It is very much alive and kicking and as soon as I have ten mins I'll do a big blog update. Unfortunately with the repairs and the huge amount of real work we have on at Hofmann's I've neglected to keep the blog up to date. We are back on the dyno @ TDI this Thursday to check the engine and get it running on sequential ignition, then next week we should be testing at Snett prior to the race the following weekend. Along with repairs I've been making some of my planned mods to improve performance too, including new brake calipers with no ABS, rose jointed wishbones and a reduction of about 20kg (although that still leaves me 20kg overweight!).

[Retset]

I'm on 400/550 and the roll is vastly reduced (thanks Chris!) If I decide to go Nitron, I will probably go for higher rates again. I think 375/475 is a bit low, especially on the rear. Thanks to Chris, I have learnt that a proportionally higher rear rate than the standard helps reduce understeer. From memory mine is approx "+70%" on the front and "+100%" on the rear when compared to OEM.

[SteveA]

[attachment=21130:Front.JPG] Here is the front one, as you can see the damping is quite soft. Chris, any advice you can give me would be greatly appreciated.

[danger7]

Hi all, I looked into several specs for my VXT suspension upgrade and settled on Nitron single ways spring rates 475F/550R coupled with Lotus Sport ARB and Komo-tec toe links and brace bar at the rear the handling is just how I want it now. Oh and an Exige S Geo. Cheers Ian

[cnrandall]

I have to say, that graph looks quite sensible Unfortunately Nitron don't run their tests down to the very slow speeds (which is the interesting bit TBO) as it takes an age but from the data you can see, Sachs aren't too far adrift. Would be interested to drive a car with a set as I havent yet.

[Sticky]

I have to say, that graph looks quite sensible

Unfortunately Nitron don't run their tests down to the very slow speeds (which is the interesting bit TBO) as it takes an age but from the data you can see, Sachs aren't too far adrift. Would be interested to drive a car with a set as I havent yet.

You're welcome to have a go in mine.

[SteveA]

I have to say, that graph looks quite sensible

Unfortunately Nitron don't run their tests down to the very slow speeds (which is the interesting bit TBO) as it takes an age but from the data you can see, Sachs aren't too far adrift. Would be interested to drive a car with a set as I havent yet.

So do you think the rates I've opted for are OK or would you suggest going stiffer? I was originally looking at 475F 600R but Nitron suggested going softer as the damping was significantly less than their 1 ways.

BTW - if you are at Cadwell Park on the 10th you are welcome to have a go.

Edited by SteveA, 01 June 2009 - 08:11 PM.

[Muncher]

I'm running 600/750 springs on my Nitrons and I'm very happy with them

[SteveA]

Nitron rebound rates are 4000n tho, Sachs are only 1300n.

[2GOOD]

I have to say, that graph looks quite sensible

Unfortunately Nitron don't run their tests down to the very slow speeds (which is the interesting bit TBO) as it takes an age but from the data you can see, Sachs aren't too far adrift. Would be interested to drive a car with a set as I havent yet.

Excellent, was worried by the silence.

[cnrandall]

I have to say, that graph looks quite sensible

Unfortunately Nitron don't run their tests down to the very slow speeds (which is the interesting bit TBO) as it takes an age but from the data you can see, Sachs aren't too far adrift. Would be interested to drive a car with a set as I havent yet.

So do you think the rates I've opted for are OK or would you suggest going stiffer? I was originally looking at 475F 600R but Nitron suggested going softer as the damping was significantly less than their 1 ways.

BTW - if you are at Cadwell Park on the 10th you are welcome to have a go.

Nitron run WAY too much rebound in their standard set-ups, which is one of the things that's different in the 'randy' spec valving that I've developed. Conventionally, most road cars will run a circa 2:1 rebound to bump ratio and more and more you will see race cars running nearer 1:1 which is what I run at the Medium/Fast damper velocities. You will find that what you can 'feel' as a driver is the 0-50mm/s range of the damper and from that graph you can tell very little about what the damper is doing.

Anyway... If you keep hold of the Sachs then I would suggest the max rate you will get from Eibach in a 2" spring will be 550lb and I would put a 400lb front with that. If you upgrade then I'm more than happy to chat through with you the different spring rate and valving options we do.

One thing to remember, even if the Sachs do produce the right sort of graphs on the dyno they will still have limiting factors because of their small body size. At a basic level, what a damper does is convert stored energy from the spring into heat and with the smaller body dampers you are limited by the quantity of oil they can hold and the piston size.

Edited by cnrandall, 02 June 2009 - 06:40 AM.

[SteveA]

Thanks Chris. TBH I think just going from a progressive spring to a linear one will make a big difference. If the springs don't give me what I want the next step was your Nitron steup anyway. Might be in touch after Cadwell

[Whiteboy]

Chris could we set up a nitron group buy with you.

[Retset]

[theolodian]

I'm on 400/550 and the roll is vastly reduced (thanks Chris!) If I decide to go Nitron, I will probably go for higher rates again. I think 375/475 is a bit low, especially on the rear. Thanks to Chris, I have learnt that a proportionally higher rear rate than the standard helps reduce understeer. From memory mine is approx "+70%" on the front and "+100%" on the rear when compared to OEM.

How do you like those spring rates on bumpy roads? I am considering GAZ Golds, but I just don't believe that 425/475 is enough of a split considering how different the front and rear axle weights are. (I know that it doesn't directly translate, but still.)