Jon Stewart Posted November 23, 2015 Share Posted November 23, 2015 My car's going to Arch in the next week or two for a chassis restoration and I was wondering if it's worth having the mounts for watts linkage added.Does anyone have experience of the change and its merits? Link to comment Share on other sites More sharing options...
SM25T Posted November 23, 2015 Share Posted November 23, 2015 I recently removed mine and changed to radius arms. The rod end bearings soon become rattly and thus very noisy. Radius arms considered the 'comfort option' by John at Redline. Fine for our extensive Euro touring. Same (front) mounts for either Watts or Radius arms. Link to comment Share on other sites More sharing options...
Alastair B Posted November 23, 2015 Share Posted November 23, 2015 Was talking about this briefly with a multi ex-Caterham owner and he was describing to me the Watts linkage and how it prevents a small degree or rear-end 'passive steering' (if you like) that you get with the radius arm from the small amount of roll you get when cornering. So his conclusion was radius arm better. Link to comment Share on other sites More sharing options...
Mavic82 Posted November 23, 2015 Share Posted November 23, 2015 Personal thoughts,. Fitted, drove it, didn't like it, removed it. If you like a very stable predictable car then it is good, ideal on bumpy roads but a bit numb. If you prefer an agile, alive car don't fit it. I also believe it is not something you want on track as the slight rear steer effect at turn in from the weight transfer to the outside wheel helps initiate the turn.however I would have the bosses added while you can, then you can decide or so could the next owner. Link to comment Share on other sites More sharing options...
griffchris Posted November 23, 2015 Share Posted November 23, 2015 Had a conversation with Derek at Caterham about this during my recent build, Watts is no longer an option on any variant aside from the 620R apparently. Link to comment Share on other sites More sharing options...
Jon Stewart Posted November 24, 2015 Author Share Posted November 24, 2015 Thanks all. I'll get the bosses added and leave it there for the time being. Link to comment Share on other sites More sharing options...
Smiffy69 Posted November 27, 2015 Share Posted November 27, 2015 Mine has Watts and I have never had an issue with it... no noise and clunky bits but they have only done 10K miles. However given I have never tried using radius arms I can't compare so my view isn't worth a lot Link to comment Share on other sites More sharing options...
SM25T Posted November 27, 2015 Share Posted November 27, 2015 Drive it more !! I replaced rod ends every two years (16k miles). Changed to radius arms around 80k. Link to comment Share on other sites More sharing options...
Simon.Rogers Posted November 28, 2015 Share Posted November 28, 2015 Doesn't slow me down. Never only had the radius arms and if stability of it makes a difference has to be an improvement on a lively car. No trouble with turn in so I don't need the passive element of the radius arm either. Link to comment Share on other sites More sharing options...
Smiffy69 Posted November 28, 2015 Share Posted November 28, 2015 Fair one Ian - yes I should drive it more ! Link to comment Share on other sites More sharing options...
150SV Posted October 28, 2023 Share Posted October 28, 2023 Possibly a stupid question - I thought all modern 7s had watts, dont know why. Anyone have a picture of the radius arm option? Whats the actual difference it makes ? Link to comment Share on other sites More sharing options...
KnifeySpoony Posted October 28, 2023 Share Posted October 28, 2023 AFAIK only the 420R race cars and the 620R come with watts linkage. Maybe the new 420cup does too. My 420R has watts linkage installed from new so I've never experienced the radius arms. Car seems plennnnty lively for me with the watts on - wouldn't want it anymore so. Link to comment Share on other sites More sharing options...
John Vine Posted October 28, 2023 Share Posted October 28, 2023 1 hour ago, 150SV said: Anyone have a picture of the radius arm option? I don't have a photo but this diagram comes from the Sigma Assembly Guide: My 2008 R400D has Watts links. This is from my build: The radius arm is, in principle, the front half of the Watts, but attached directly to the De Dion. JV Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted October 28, 2023 Share Posted October 28, 2023 48 minutes ago, KnifeySpoony said: AFAIK only the 420R race cars and the 620R come with watts linkage. Maybe the new 420cup does too. My 420R has watts linkage installed from new so I've never experienced the radius arms. Car seems plennnnty lively for me with the watts on - wouldn't want it anymore so. It is certainly common, if not standard, on all R400D and R500Ds. Link to comment Share on other sites More sharing options...
Area Representative paul richards Posted October 28, 2023 Area Representative Share Posted October 28, 2023 Watts linkage was standard on all the sportier versions e.g. Superlight. More expensive and I understand rose joints are prone to wear and hence needing to be replaced fairly regularly. Essentially allows the mount on the top of the de dion tube to move vertically rather than in an arc. I think you’d need to Lewis Hamilton to notice any improvement in handling. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted October 28, 2023 Leadership Team Share Posted October 28, 2023 My car started with the Watts link setup and now has radius arms. I see no reason to go back to a Watts link. Stu. 1 Link to comment Share on other sites More sharing options...
KnifeySpoony Posted October 28, 2023 Share Posted October 28, 2023 (edited) 6 hours ago, aerobod - near CYYC said: It is certainly common, if not standard, on all R400D and R500Ds. I mean on current model cars. I think all the superlight series cars came with watts. Edited October 28, 2023 by KnifeySpoony Link to comment Share on other sites More sharing options...
ECR Posted October 29, 2023 Share Posted October 29, 2023 I seem to remember that non watts link cars create rear toe (in? Out?) aiding initial turn in …. Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted October 29, 2023 Share Posted October 29, 2023 9 hours ago, ECR said: I seem to remember that non watts link cars create rear toe (in? Out?) aiding initial turn in …. There is a smaller effect of rear steer as the outside suspension is compressed and the radius arm moves away from parallel with the ground, but as the inside wheel also moves away from parallel this will be counteracted somewhat. Another effect of this will be a slightly lower grip, though, as the slip angle increases. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted October 29, 2023 Member Share Posted October 29, 2023 Felt like a good opportunity to test an animated GIF on the new website. Jonathan PS: It's either Watt Linkage or Watt's linkage. : -) 6 Link to comment Share on other sites More sharing options...
Area Representative Geoff Brown Posted October 30, 2023 Area Representative Share Posted October 30, 2023 Having owned two Sevens with just the Radius Arm fitted & now owning a Seven with Watts Linkage, for the last 10 years all I can state from driving is that the rear end of the car is more focused & tight. It follows the front end round as if on rails with little if any of the wayward sideways feeling of a Radius Arm only rear suspension. Also the limit seems to be more apparent before attempting to disappear into the vegetation ! The car in question is an R400D with 13" 8J rear wheels. All four wheels have been shod with both CR500 & currently ZZS. Obviously opinions will differ but that is my seat of the pants appraisal. Link to comment Share on other sites More sharing options...
Area Representative Geoff Brown Posted March 11 Area Representative Share Posted March 11 Out of the blue & via club admin I recently received this email from Clive Roberts the co creator of the Watts linkage system as fitted to the Seven. He had read my comments (above) & in some ways endorses my take on how well a Seven handles with the system fitted. Geoff - I was interested to read the comments on the Watt linkage from October 2023. As the co-creator of that system, perhaps I could add some detail? The purpose of the system was to reduce the steer angles caused by the single radius arm. This is more acute than with a more typical 4 link axle system because the lower A-frame, pivoted on the axle centre, plays no part in the roll steer - so the axle steers at the command of the radius arm. This is short and thus powerful. I discussed this many times with the inimitable and much-missed Reg Price, we felt that a small amount of steer could be helpful in level cornering but the base system was just too much considering bumps, mid-corner braking and other real-life events. Hence the Watt system. While we built the first version with zero steer, the concept was to have proportions adjustable to introduce an amount of steer if needed. We were conscious that zero steer might feel a little inert to a person accustomed to the standard system. I had left Caterham and was working in the US by the time the first car was equipped with the system. I met up with Reg and Rob Nearn at Thruxton for the first test. Rob ran his car in standard form as baseline, we then fitted the Watt system and he ran it with no other changes. On his second lap he was 2.4 seconds faster than baseline, commenting that the new system allowed him to take lines across mid-corner bumps with confidence that he wouldn't be bumped off line. We took this as a good result and I continued with my holiday. I don't know what further development was done, if any. I was surprised to see that people have problems with rod end life - I thought they were only to be used for development purposes, I didn't expect them to see road use. A final thought - the Watt system was very effective in controlling unwanted axle movement in the late 80s, when we were using horribly crude Spax dampers. The advantage might be reduced with more capable dampers but I believe the improved geometry will always be useful, somewhere. Best regards Clive Link to comment Share on other sites More sharing options...
AlastairA Posted March 11 Share Posted March 11 Photo of radius arm on my 2023 420R: Link to comment Share on other sites More sharing options...
Ainsley Posted March 11 Share Posted March 11 How does it affect the car if you use the upper mounting point for the radius arm instead of the lower mounting point. In the "instructions" it says S for the top and R for the bottom. But I wondered why and what is the difference. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted March 11 Member Share Posted March 11 3 minutes ago, Ainsley said: How does it affect the car if you use the upper mounting point for the radius arm instead of the lower mounting point. In the "instructions" it says S for the top and R for the bottom. But I wondered why and what is the difference. The Assembly Guide used to say for the radius arm option: NOTE On some series 3 chassis a lower fixing boss is supplied to give optimum suspension geometry when used only for race and track purposes. This setting is not recommended for road usage. Jonathan Link to comment Share on other sites More sharing options...
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