10 replies to this topic

[Turbo van]

Simple can you lighten standard radius arms without weakening them if so how fanks

[Sam Walters]

In a word. Nope. You cant pal. You can always build more out of t45 steel using rose joints. You just need to make a jig up.

[samsfern]

Or buy some alloy ones from KAD....

[samsfern]

http://www.kad-uk.co...4&product_id=22

[Tahiti Joe]

Or some from Specialist Components, seen some fitted, very very puurddyyy!

http://www.twinkam.c...hop_param=cid=

[Sam Walters]

The KAD ones are weak.

[mike.]

The KAD ones do say light road use. Although it says heavy circuit use and rallying. At first I thought yeah maybe because of potholes they're only for light road use, but how can they be suitable for rallying and not road use?

The SC ones are nice but for coilovers only, KAD works with rubber cones

Edited by mike., 19 February 2012 - 12:40 AM.

[Tupers]

Technically you can lighten cast iron arms but not by a huge amount. I went over Mine with a 60 grit flap disc on the grinder and will be finishing them with the DA to get rid of the casting marks and was surprised at how much material actually came off.

[tiger99]

Polishing off the rough bits improves the fatigue life, and is a good idea, as long as you do no more than take off the rough bits to get a smooth surface. A bit like polishing con rods and cranksafts, it removes stress raisers. What Tupers has done in the photo is ideal.

Alloy radius arms are positively dangerous for road use, as they have a very limited fatigue life. The mileage accumulated in circuit use is relatively small, so they should be ok, but a road car may accumulate upwards of 100k miles.

The standard steel radius arm is not all that heavy, and any performance gain from weight reduction would be minimal. It is only partly unsprung weight, and that can be improved far more by restricting the wheels and tyres to sensible sizes. The biggest contributor to unsprung weight in the radius arm is the hub end, and you can't reduce that very much, considering that most of the weight is in the stub axle, brake drum and backplate.

Oh, and they are cast steel, not cast iron.

Edited by tiger99, 19 February 2012 - 02:58 AM.

[Turbo van]

Thanks for that guys on a tight budget so I think I will go with cleaning up the old ones they will be on a beam so I was going to cut off the knuckle would this still be safe

[tiger99]

Yes, the knuckle can come off if you are not using it.