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Bigger wheels or change gearbox ratio?

3K views 4 replies 3 participants last post by  remifromnottingham 
#1 ·
Hello,

First post, been reading the forum since getting a 112cdi in September. I'm converting it into a campervan.

I find it too powerful for my needs, as it not lugging a pallet of bricks! Meanwhile, the gearing ratio is not what i would choose to have for a vehicle with 5 gears only. I find that i need to change gears earlier than surrounding traffic when pulling from a standstill, and to drive it at 70 mph the engine is revving too close to 3000rpm to be economical.

First thought was that there might be a way to change some gearing in the gearbox,

Then i realised that fitting bigger wheels would achieve the same effect, at a fraction of the cost.

What do you guys think? To sum it up, i would like to use some of the torque to keep the engine running at lower rev. The van has only 53k miles with full service history, so there's no need to overhaul the gearbox in this lifetime! It will have a new paintjob done soonish, so if there need to be some modification to the wheelarches, they can be done at that time for (hopefully) little added cost.

Thanks for your help,

Remi
 
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#2 ·
Hi Remi, just under 3000 at 70 is about right for the manual and about 2750 for the auto. The cut off point for economy is 3000 revs because after that it is making turbo boost all the time even when you back off the throttle.53K It is only just run in, im on 239000K and still going strong. Bigger wheels if you can find them would make sense but think about how much bigger, when i had new tyres fitted that had about 6/8mm more tread it made 300 revs difference on my gearing so going to much bigger could make it work harder especially in windy conditions


Cheers Martin
 
#3 ·
Thanks Martin, 8mm more thread giving 300rpm difference, that's quite a lot.

My van has 195/70/15 tires. I am wondering if fitting 16" rims with "normal" size similar tires would work? I find that the wheels look a bit small compared with the size of the wheel arches. Maybe the passenger version of the vito have larger wheels?

Cheers,

Remi
 
#4 ·
In Denmark, where I live, theres a limit to how much you may increase wheel diameter - I think it's 5%.

I own a Viano - originally fit with 205/65-16, but my summertyres are 235/55-17 - which gives me a little reduction in revs, a more precise speedometer - and a nice look ;-)
- all within the limits. Mine is 6-speed - at 110km/t (app. 70mph) it revs around 2500rpm.
 
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