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For those who could be interested, I fitted a set of 19/20" PB Racing wheels on my S IPS '12.

They look very good in matte black, especially on an Aspen white Evora.

img0876dd.jpg

The best thing is they are lightweight compared to diamond cuts and I can really feel it (-3kg per front rim and -1.8kg per back rim). I'd lost a bit of road feel when trading my LE for this S IPS, and it's back!

The car feels more lively, the acceleration a bit more immediate. I'm very satisfied.

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That's interesting re the weights. I'll have a look on their site and see the cost. What is your logic for it feeling faster, just the weight?

Trevor.

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Lionel, I could be interested, though I'd want to know more about their quality, e.g. why they say "decrease the comfort level". Plenty to investigate. (Same bolts?) And of course whether the finely tuned Lotus suspension might be adversely affected.

Leaving all that aside, what matters to me is the effect on performance and your comment that you can feel the difference.

I had thought about the Lotus forged wheels previously and so I obtained precise weights for them and for the standard ones, via Lotus, from the manufacturer. (l didn't ask who.) BUT it was for the 18"/19" combination and I did not ask for the 20" weight. I put the numbers into the Techwiki on "another forum". Anyway, I know they are right: 10.4 Kg 18" front and 12.6 Kg 19" rear. I won't confuse things here with the figures for the forged ones - see the Techwiki - but they are very little lighter and I dropped the matter. (Expensive too!)

The weight savings you mention are much more interesting and I've done some research. I discovered a site that includes a calculator. In fact it is a very informative site, although with a warning - numbers at your own risk!

We know that it is rotational inertia that counts for acceleration and not simply the dead weight of the wheel but an Equivalent Mass of dead weight that would have the same effect - always greater. (Lower unsprung weight also helps with the feel you mention too, of course.)

There are some unknowns and I had to assume for instance that rims represent 65% of the mass of the wheel. Also of course I do not know the weight saved by PB wheels for their 18" size. But based on the figures you give, I have assumed that it is the same 3Kg as for the 19". The results are below. Of course they don't apply to your car, but they do illustrate the kind of effect and that it is greater than the dead weights.

Standard 18": Wt.10.4 Kg Equiv Mass: 14.5 Kg. Standard 19": Wt. 12.6 Kg Equiv Mass: 18.14 Kg.

PB estimated 18": Wt 7.4 Kg Equiv Mass: 10.32 Kg PB estimated 19": Wt. 9.6 Kg Equiv Mass: 13.82 Kg

Totalling up gives Standard: 65.28 Kg. PB estimated: 48.28 Kg.

Thus for a NA car that is effectively 17KG saved. That could indeed be noticeable.

I intend to spend more time with the site I found; it has the basic maths and seems pretty good, covering tyres - and bolts - too. Anyone else inclined, see: http://hpwizard.com/...al-inertia.html

Edit: Cost for a set seems to be just over the £1K, though I don't know about VAT on that. Not too bad.

Edited by mdavies

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Interesting stuff Mel. I would never have believed it would make that much difference but stand corrected. My only experience of heavier wheels was on a Mondial that I had fitted aftermarket 16" wheels to save the cost of expensive metric tyres. Shortly after I came across a set of genuine 16" Ferrari wheels and swapped to these. What a difference, lighter steering with life rather than a dead feel. Didn't notice a performance gain though.

http://m.youtube.com/watch?v=X9TyxoZOwz8

Trevor.

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I haven't noticed a difference in comfort, and the suspensions are set up for the standard 18/19 as well as the heavier 19/20, so I guess that wouldn't make much of a difference on the car's behavior. If you want exact weight savings on 18/19, ask Danilo Moroni from PB Racing, he answered my questions.

The only other picture I have for the time is this rather crappy one, I'll make some more asap.

img0855om.jpg

About the performance, I didn't mean the car was actually faster, but it's more immediate at the moment you put your foot down.

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Must say those wheels do look good. I've also been considering 19"/20" wheels for next year. The Diamond Cuts are insanely expensive, whereas the BP Racing wheels are quite acceptably priced. If they are lighter that would be a fruther incentive to go that way.

I believe they may actually be from BBS, but to PB Racing's custom specification for the Evora.

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About the performance, I didn't mean the car was actually faster, but it's more immediate at the moment you put your foot down.

Lionel, putting my approximately calculated 17 Kg in the context of an NA weight of 1380 Kg gives a reduction of about 1.2%. So, for the performance orientated people who have their NAs up to 300 bhp already, and being conservative about the assumptions I had to make, that gives the effect of having 303 bhp at least. It's acceleration that would gain, not top speed of course. Although it doesn't seem much, possibly you could feel it.

Re any effect on the suspension, as there as some substantial tyres involved too indeed it would be surprising if the weight reduction was significant.

Suggestion (for Bibs?): Assuming Lotus needs every penny at the moment, how about asking whether some of their technical specialists would be prepared to give lectures/discussions to paying groups on topics of interest?! Before spending £1K plus on modifications, I'd be happy to pay say £50 to hear advice from the horses mouth! (And warranties have started to expire!) Ok, it wouldn't produce the Esprit, but wouldn't there be a PR payoff?

Edited by mdavies

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Not yet Justin I've had loads of work lately.

I'll try to find some time soon to make some ;)

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Although I normally put performance above all else, I must admit they do look good!

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Coming back to this thread, does anyone have experience with these wheels regarding their certification?

 

In Germany all non-OEM parts must be certified for use on the vehicle and be listed on the car's registration. I spoke to PB Racing on this, but the do not seem to have any experiences outside Italy. The information they did provide will never satisfy the TUEV.

 

What are the regulations in France or UK? Or, if anyone in Germany has these wheels that would be a great help.

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In the UK, add anything you like to the car, I'm pretty sure it's unregulated and as long as it passes an MOT, you're fine on the whole. The Police can enforce 'Construction and Use Regulations' at the roadside but I've never known it to happen and it's unlikely they'd know one wheel from another anyway.

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I was very interested in the PB wheels after doing the sums above, but held back on worrying about strength, approval, insurance issues. On the PB site I read as below from a page re their wheels, albeit in connection with sport:

 

"Remember that all the non-original products imply the re-homologation of the car. Motorsport is dangerous"

 

It's the slight chance of say a hard kerb impact that causes fracture, loss of control then whatever.  Given that non-OEM wheels are widely fitted by the likes of us, I wonder whether there has been any "case law". (Assuming that insurance has given modification approval - on your own without that.) 

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Pretty much any upgrade you buy from Lotus Racing in Hethel will say 'for track use only', even a Stage II exhaust! 

 

No-one will warrant against failure from driving into a kerb either, not even OEM wheels. They're not made from adamantium! 

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I guess the strict laws over here in Germany are the downside to not having a general speed limit. Cars will reach very high speeds much more often over here. Since all changes have to be documented the Police can and will enforce these regulations strictly, as will the TUEV (our MOT). :busted cop:

 

Of course, with a very rare car such as a Lotus your chances of getting through are better, but then I still want the confidence the wheel won't crack when I'm doing 290 KpH :no  

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Quote playing up, but Bibs: "No-one will warrant against failure from driving into a kerb either, not even OEM wheels."

 

The wheel is not the point. It is a failure - that arguably might not have happened with a standard wheel - pitching you to a head-on across the road. Failure of many items (eg exhausts) are not likely to have such consequences.

Edited by mdavies

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How do you prove that the orginal wheel would have survived?

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How do you prove that the orginal wheel would have survived?

That is why there is such a complex certification process before Lotus can sell the car. Or, as in the case of the Elise NOT sell the car in the US.

 

The difference is that whilst you can quite liberaly modify the car once you hav bought it in the US, that is not the case here. Evere modification with potential safety relevance must be approved by an independent certified agency. In Germany this is generally the TUEV, but there are EC-norms and agencies that are also sufficient. For most mods on most cars there is a so-called type-approval for the modification, but the Lotus market seems too small for this. For example, the PB Racing do require individual approval, which is a costly and complex process over here - in the end you are at the whim of the assessor.

 

So, coming back to your question, of course there is no way to prove that the original wheel would have survived. But, you can prove that the OEM wheel was tested and certified according to all applicable standards and approved for use in your car.

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How do you prove that the orginal wheel would have survived?

 

Not necessary to prove.  I said arguably . If non-standard, unless approved, you are in trouble.

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I love the 19/20 setup. Do you have more pictures you can post? I was thinking of getting a set.

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