15 x 7 alloy wheels with a - 10 mm offset on a Range Rover Classic SWB

[RRC200Tdi]

I have an opportunity to purchase some used wheels that need refinishing. I am a bit intrigued and tempted by them, probably because I have never seen them before, which is about all the encouragement I usually need. They are 15 x 7 inch with a -10 mm offset. I am currently running Tornado/Freestyle wheels from a NAS Defender, with what I believe are a +33mm offset. I have OME heavy duty springs installed which yield a little over 1 inch of lift. I have 265/75 r16 currently on the vehicle and would like to run 31 x 10.5 with the 15 inch rims, which are similar in diameter and width. I am completely happy with how the vehicle drives right now, but I have never been very enthusiastic about the stance and always wanted to widen it a bit (but I am not comfortable with going with spacers, but that is a topic for another day). I am afraid that a -44mm offset change is going to be a little too extreme (~1.75" per side). There are numerous benefits with going with smaller wheel diameter and higher sidewall profile--well, actually the 31 x 10.5 tires are in reality 30.6" and my 265/75 tires are 31.7", more than cancelling out the increase in sidewall height. I guess I could go up to 33 x 10.5. Anyway, has anybody fitted -10 offset wheels with a similar tire size on their classic? Were there a lot of problems with clearance? Below are the wheels in question. I have never seen this style before. Anyone familiar with these? 

 

 

Thanks!

[Escape]

The popular steel wheels like 8-spokes and modular are available in -8 or -10mm and are used frequently on Range Rovers. I used those on my Defender (in 16" but that wont make any difference apart from choice of tyres). So you should be fine. If you go for 33x10.5 you might have to look at clearance with the outer edge of the wheel arches on full compression, also depending on actual tyre width. I can certainly understand your desire to fit smaller rims instead of bigger as on so many moderns. 😉

Filip

[RRC200Tdi]

Thank you for inspiring some confidence! Now I just need to take the plunge and commit to buy. I have near new BFG mud terrains on my 16s and don't want to have to fork out more money for another new set of tires, but, long term, equivalently sized tires are quite a bit cheaper on the 15s as opposed to the 16s. Going an inch smaller in diameter will also reduce rotational mass and improve gearing, both of which would increase effective power and fuel efficiency.

'I can certainly understand your desire to fit smaller rims instead of bigger as on so many moderns.' <- you truly hit the nail on the head here

[Escape]

6 hours ago, RRC200Tdi said:

Going an inch smaller in diameter will also reduce rotational mass and improve gearing, both of which would increase effective power and fuel efficiency.

Just to be clear, wheel size does not have a direct effect, only the tyres fitted. So yes, if you go from 265/75R16 (about 32") to 31x10.5-15 you will have a 3% difference. Or the other way if you go up to 33x10.5-15. 3% is not much anyway! It may be noticeable when driving off with a heavy trailer, but wont make much difference in normal use.
As for fuel economy, that depends on a lot of things, like the state of the engine, usage, prefered cruising speed etc. At moderate speeds on the motorway the Tdi could prefer slightly lower revs so economy could suffer with smaller tyres. Which is why some fit an overdrive or (like myself) prefer a long 5th gear for cruising. Then there's also other stuff influenced by tyre size, like the ride height and aerodynamics. As long as you only go up or down one size, other factors will be more important, like the look you prefer or price and availability of tyres.

Filip

[RRC200Tdi]

Great points, Filip. With regard to my thoughts about efficiency, I haven't had the chance to weigh my wheels or know the weight of the 15 inch ones I am considering, but I remember there being quite some difference between 16" and 18" wheels on my P38. I don't remember the actual values, but the 18s mounted with tires weighed a meaningful bit more than the 16s with roughly the same width and diameter. I didn't do any scientific testing, but the general pattern was 18 -20 mpg (US) on the highway with the 16s and 15-17 mpg with the 18s. I inferred that it must of been a result of the difference in the metal to rubber ratio. Those differences seem like a lot, perhaps there were other factors in play that I was not aware of. So, I guess I am expecting a similar outcome, albeit less with only an inch difference. I completely agree with everything else you said 🙂

'Or the other way if you go up to 33x10.5-15. 3% is not much anyway! It may be noticeable when driving off with a heavy trailer, but wont make much difference in normal use.' <- I think this and your overall point is very important to keep in mind. I won't really notice a meaningful change. I had thought that a little smaller tire might make the enormous hills I have to negotiate on a daily basis a little bit easier on the 200Tdi. The other advantage of going with a smaller wheel is that given the same overall diameter and width of the wheel/tire combo, you will achieve a greater contact patch when airing down for off roading. I didn't mention it because I realized that the 31 X 10.5 x 15 would actually have the same sidewall thickness as my 265/75 16 tires 😞  

Unfortunately, 33 x 10.50 are about the same price as the 265/75 tires, so no benefit there.

-jack

[Escape]

Hi Jack,

If you need to tackle a lot of hills, smaller tyres will help. Even if it's only a few %.

I find it hard to believe you got such a difference in economy just from wheel weights. Were the tyres fitted the same width and overall diameter? A lot of people forget that when going to bigger or smaller (diameter) tyres, the speedo reading is also affected, so the distance recorded will change. Also, I don't think on a slow and heavy 4x4 tyre weight will have much effect. Unless you'd go from a a hi-tech alloy wheel with a small roadtyre to a solid steel one with a massive knobbly tyre. 😉   
A friend did some testing on his Lotus Exige V6, comparing stock wheels to track-spec light weight ones. There was some difference, but it was minimal. And not so much on outright speed/acceleration (fuel economy was obviously of no importance but would be similar), but a just noticeable effect on inertia when changing speed and direction. None of which is a priority for a Land Rover.

Just chose whatever you like, it will be fine and you'll be happy 'cause you like it. 🙂 I can be very fussy about tyres myself, it can make life difficult sometimes.

BTW, great pic of the airbourne P38! Care to share the story? I've had mine on just one wheel at the end of a steep slope offroading, but unfortunately no pics or vids... I was one of the few vehicles to make it up there though! And conveniently forgot I had a 400mile drive home when I floored it to prove a point...

Filip

[missingsid]

Will 15 inch wheels clear the brakes?

[RRC200Tdi]

"I find it hard to believe you got such a difference in economy just from wheel weights. Were the tyres fitted the same width and overall diameter? A lot of people forget that when going to bigger or smaller (diameter) tyres, the speedo reading is also affected, so the distance recorded will change. Also, I don't think on a slow and heavy 4x4 tyre weight will have much effect. Unless you'd go from a a hi-tech alloy wheel with a small roadtyre to a solid steel one with a massive knobbly tyre."  <- The tires were both street tires, the 16s were Michelin LTX A/T2 and the 18s were Premier LTX, so roughly similar. I was thinking about it and I had a similar difference with my BMW E36 M3, where I would get 33 MPG with the stock wheels which were 17 inches and somewhere between 27 and 29 MPG with aftermarket 18 inch wheels (I don't remember the exact mileage with the 18 inch wheels but it was almost the same as my toyota camry which got about 27 MPG). Maybe my driving habits change with the larger diameter wheels 🙂  Otherwise, I really don't know, it was never a scientific comparison. These observations were made when I used to commute 45 miles each way everyday over 3 steep grades up and down. Maybe hill climbs played a role? 

Thanks for the compliment about the jump. That is actually my 1989 classic although it does look a bit like a p38 in that tiny picture! I used to jump it regularly. That was actually in my backyard back when I had some land. I actually had repaired my mitsubishi montero one day and wanted to drive it over this bank in my backyard and I accidentally got the front two wheels off the ground. Well, when I installed some old man emu shocks and springs on my classic I just had to give it go. That picture was actually a still taken from the video of it (i'll post it if I have it) and was my second attempt. It sort of became a carnival ride for whomever was visiting. Well as these things tend to do, it eventually got out of hand. The last time I did it I was going way too fast and I jumped way too far. There is no picture or video, but it was crazy. When I landed I the steering was horribly off. I limped it over to my work area and found the tire bead had jumped off the rim, but worse both front wheels were noticeable towed out. Turns out I caved in my front axle housing and popped out my Old Man Emu caster correction bushings! Fortunately I had a spare axle with upgraded 24 splines waiting to go in and spare set of radius arms, so I quickly repaired it the next day, as i wanted to move on from this disgraceful incident as soon as possible. I never ever attempted it again!

 

 

Edited April 3, 2021 by RRC200Tdi
fixed the video link

[Escape]

10 hours ago, missingsid said:

Will 15 inch wheels clear the brakes?

I've seen a few RRCs on 15" wheels, so it's definitely possible. I don't think the size of the brakes changed much over the years.

[missingsid]

22 hours ago, Escape said:

I've seen a few RRCs on 15" wheels, so it's definitely possible. I don't think the size of the brakes changed much over the years.

Thanks.

[Snagger]

There is no way that having higher or lower profile tyres and wheels of the same outer diameter is going to give those fuel economy differences.  As Filip mentioned, any difference in rolling diameter is going to affect the speedo and odometer readings, so a bigger diameter will record less miles for the same fuel used, and may result in higher fuel burn anyway because the raised total gearing is too high for maximum efficiency, the gear box being in lower gears for more time and the engine labouring harder, especially if driven at the same indicated speed (ie actually faster).

Also creating a lot more rolling resistance would be wider tyres, aggressive tread pattern, lower inflation pressure and softer rubber compounds.  Those are all very likely candidates for the increased fuel consumption, especially pressure.