Just about to order a new pair of tyres and the guy in the tyre shop got me thinking. What WAS the OEM spec for the BRM. The Driver's Manual isn't much use as it doesn't cover the 205/45 16, but reading my pristine original sales brochure (any offers?) I see 16" with 205/45ZR. What speed rating does that equate to? When I checked I've got two different speed ratings on front and rear at the moment!
Wonderful thing, the internet. I've just found that ZR is the highest speed rating for more than 240 kph. That seems a little extreme. I would have thought H (210 kph) would be quite adequate. Anybody ever been picked up at the MOT?
I don't think the Dunlop tyre specified is is available anymore. That said, @peasantslife will no doubt ( or someone else) will point you in the right direction.
Depending on ones point of view, if an insurance company ever wants to find a reason to not pay out, it could be classed as not having original spec / undeclared modification on your vehicle if you go with a different rating? There seemed to be a spat of this being circulated a few years ago at least, along with the use of winter tyres, but I don't know how much grounding it has in reality. That all said... I thought the ZR-rated tyres was only applied to the R3 once MG-Rover launched... The ironically named ZR? I thought the BRMs had a lower rated tyre and a quick lookup on Black Circles suggests a W rating? I've also searched for a couple of websites to see if I can find the rating of the Dunlop's but I'm not finding anything less than a 215/45/16.
Read the column Speed Rating (Up To....) As you can see, a BRM's Vmax sits 1mph above the H class hence it was fitted with V rated tyres by Rover. In my personal adventures in continental europe when racing south in Germany I've found the car will make something above 7200 in 4th which is - according to sat nav into the mid 130's, so well past the H class maxima. In the UK currently its not a criteria that is actually inspected at MoT, though certainly there are plenty of opportunities to fail on tyres! Of course one may take the view here that getting anywhere near 130mph is about 60mph (100kmph) over our speed limit, so somewhat foolhardy to attempt, in which case an H rated tyre may be fine - even for an insurance assessor. However in other regulatory jurisdictions in europe that would never hold water. You also need to be aware of your tyres load rating, well a BRM 5 up with boot and roof luggage, a full tank of fuel and max trailer nose weight could well be approaching 2 tonnes, so probably worth not going under 85 load index as that gives you a 500 kilo per tyre capability - entirely pointless if you dont know the pressure to run it at! (possibly 45psi (3bar for us continentals)). Tyres a black art even within the industry, not many petrolheads actually know much about at all. The extent to which we test tyres would simply confound belief, and it is a task which is still ultimately determined (signed off) by just a few highly skilled driver engineers. Lets just take a typical scenario, the brand has a reputation to maintain yet the car in question comes as standard of 2 or 3 rim widths, and sizes ranging from 16" for rental fodder to 21" boy racer. Its available as diesel slogger or supercharged V8 in floppy convertible body, saloon or estate holdall. May have two tyre brands for differing global markets, now go and get that lot into an alignment of progressively improving dynamics, all of which meet the brand expectations for responsiveness, fuel economy, life, grip, NVH. O'h and dont forget these guys tell us what pressure it needs to run at, and can actually tell which corner is down or up by a single psi!
Thinking about it, probably best if I fit 2 new tyres to match the speed rating of the 2 tyres I'm keeping. I don't think it will be a problem for the MOT, but I certainly wouldn't want to raise any questions in the mind of an insurance assessor should the worst happen!
Try to match your others too ,but not always possible ,so keep any different ones on the same axle ,also keep your new ones on the front ,less chance of blow out and more wear on the front .
Yup! Always do. New tyres on the front, then move them to the rear as they get worn on the inner shoulder.
The other brochure agrees! Maybe the more recent Dunlop Sport Maxx tyres had a different and that's what I'm remembering? But that also means the online checkers are also wrong?
Yes.... Since I have access to the lions share of DVLA data now, I can confirm that I dont see a homologated Vmax for BRM,s. so we have to rely on Rovers quoted 131mph. And just to reiterate on a tyres load index, the declared BRM ULW (Un-Laden Weight) is 1025 kg. but its homologated GVW is 1550 kg. Perhaps handily if you get stopped hauling a Hobby or Bursteiner twin-ax off the traveller site there is no Gross Combination weight. Sarge will have to make a quick mental judgement on safety. But be aware that in the UK we have a 7ft 6inch towball-drawn max width trailer, so any of those wider continental jobbies will still get you in trouble (they build to continental 2.5m / 8ft 2inch regs)
