Increased tyre sizes

[BenDover]

I am looking at getting some new tyres for my widetrack Feroza. I want to go a little bit larger diameter but not too large so as to require a suspension lift!

I want to change the gearing so that when cruising on highway it is not revving it's tits off so much. Perhaps have it rev about 3k or 3.2k on 100?

Which tyre size would you recommend for this? The ones on there now I think are the stock which are 225/70/15.

Cheers,
Ben

[FeroZul]

You can try going up to 235/75/15.

How many RPMs are you sitting on at 100 km/h?

My feroza sat at ~3100 RPM at 100km/h on the stock 225/70/15s, but that's with an extractor and exhaust job. If your tires are still good, maybe that's an option for you instead.

[BenDover]

Are you sure it sat on 3100 rpm with the stock tyres? Mine sits on around 3600-3700 at 100 and I have read that that is the standard.

I have extractors on it now but I wouldn't have thought that it should change the gearing as it has nothing to do with that. It would only affect the efficiency and power of the vehicle.

I have priced some 235/75/15's and also some 225/75/15's and they are the same price. If I want to stay legal I have to go for the 225/75/15's. Any thought's on which is best? Would the 235's rub on full lock? Anyone else done this?

Cheers
Ben

[murcod]

Even if you fit larger tyres your speedo will still read the same speed at the same revs- it will just not be accurate any more. Extractors etc will not have any affect either, they only affect engine power.

This may help you out:

http://www.outerlimits4x4.com/PHP_Modul ... peedo+tyre

There are also various tyre size vs speedo error calculators at web sites- try searching on google.

Don't forget you'll kill your acceleration by fitting larger tyres and will need to change down for hills more often.

[FeroZul]

Are you sure it sat on 3100 rpm with the stock tyres? Mine sits on around 3600-3700 at 100 and I have read that that is the standard.

Ben

mmmm... i must have seen it wrong then!

will get on the freeway later and check again...

[BenDover]

Murcod: If I fit 235/75/15's in place of 225/70/15's this shouldn't affect the power all that much should it? Yeah I know it will put the speedo out a little bit but my main priority was decreasing the revs when travelling at 100 (not going by speedo's 100). Will this do it?

[HeathGQ]

geez only just Ben..... I had 30"s on mine, but as I said, I found I still did 100 on the speedo cause it just cruised well at thse revs (approx 3900 - 4000 rpms). It was about 10% out, so 100 on the speedo was 110.

No matter what you do, it will not rev lower - thats the way they are...

[murcod]

IIRC 235/75 doesn't make that much difference at 100km/h ?

[BenDover]

How much of a difference do you think it would make? If it doesn't make very much difference then hopefully it should make even less difference in the lower revs with acceleration?

My theory is that the engine will last longer if I can stop it from revving so high along the freeway.

[murcod]

235/75R15 will give a speedo error of only 5.4% according to this link : http://www.miata.net/garage/tirecalc.html

So, roughly whatever revs you're doing at 95km/h now, will be what you'll be doing at a real 100km/h with 235/75R15 tyres.

[BenDover]

Cool. Thanks for the link. That's an awesome reference site!

I think at 95k's it's doing about 3400rpm so that would be a bit better than 3600-3700. A lot better for cruising along the freeway.

Any idea if that size would rub at all? Anyone else already running that size tyres?

[built4thrashing]

when i had the 31s on my feroza 88km on the dash was actually 100km/h on the road and the revs were only 3100.

[Dangerous Dave]

Is it possible to fit 33" on a feroza. Now when I say possible. I have a 4 inch lift at least and i am willing to use an angle grinder. Know of anyone who's done this?


Should I get my own thread?


Dave

[SimplyPV]

not without changing your gearing bro... you would have shit for acceration and likely burn ur clutch out REAL quick... if you go any bigger tahn 31, your diffs and cv joints wouldnt last very long thats for sure. the engine itself is solid but the tranny is whole other story. want bigger than 31's? do a SAS and SPOC and you'll be able to run almost any size you want as long as you got an engine that can turn em.

[rOd]

I have a 4 inch lift at least
Dave

Interesting

[SimplyPV]

I have a 4 inch lift at least
Dave

Interesting

2 inch body and 2 inch suspension (torsion bars) i thinik... 2+2=4....

[4x4roza]

without a body or suspension lift going any bigger then 235/75/15 you will rub tyres, i had them on with the car stock and it was ok, with just the 2inch body lift i had 30/9.5/15 muds on sunraiser rims and it was rubbing due to the different offset of the rims, now with the 2inch suspension lift i have no trouble with them.
if you wanna change your gearing you can change your diff ratio but you must relise that to check lower high speed revs you will loose take off power, and i wouldnt reccomend it cause they already have no power as it is.

[murcod]

if you wanna change your gearing you can change your diff ratio

Where are you planning on finding new diff ratios for a Feroza?

Dave, since when have you had a 4" lift???

[Dangerous Dave]

I've had 4 inches for a while now. I made up a 2" body lift using some nylon rods i got from Consolidated Bearing Company. My mates dad has a lathe so i used that. Nice and easy. I also got some oversized 1/2 inch Grade 8 hi tensile bolts and drilled out the body. She's not going no where. I also wound the front torsion bars up and "customised" the rear shackles. Although the springs are starting to sag. I'll have to start saving for a new pair!


Dave.

[*BESTY*]

Is it possible to fit 33" on a feroza. Dave

YES.........you could probably fit 38's on your Feroza...............BUT........

































Don't expect to be able to drive it.....or turn the wheels !!!

[icebreaker]

235 Muddies do me well


30's or 31's would be nice.. but 29's and then a lift kit will suffice..


The lift will come eventually...

[rocknferoza]

235/75's are fine with standard lift and swaybar still connected.

If you do alot of driving on rough roads I would leave the swaybar connected. If you remove it you'll find that your front tyres will rub on the plastic on the inner guards.

Just my 2 cents worth

[rocknferoza]

Something else worth considering is changing 5th gear as the gears in the feroza and charade gearboxes are interchangable
Would be a good mod but I would only suggest doing it if your gearbox needs work.

[rOd]

Something else worth considering is changing 5th gear as the gears in the feroza and charade gearboxes are interchangable
Would be a good mod but I would only suggest doing it if your gearbox needs work.

Now thats thinking outside the square!

IF the Charade's gear ratios are lower, then this might be a way of getting lower ratios.

[HeathGQ]

Something else worth considering is changing 5th gear as the gears in the feroza and charade gearboxes are interchangable
Would be a good mod but I would only suggest doing it if your gearbox needs work.

i asked that wehn I got my gearbox re-built. Maybe he didnt know enough about em, but the dude just said no

[Oferoza]

charade gear ratio:
1st: 3,500
2nd: 2,111
3rd: 1,392
4th: 0,971
5th: 0,794
Reverse: 3,538

just if you want higher final speed change the 5th gear, otherwise i don't see any improvment.

oferoza

[SimplyPV]

235/75's are fine with standard lift and swaybar still connected.

If you do alot of driving on rough roads I would leave the swaybar connected. If you remove it you'll find that your front tyres will rub on the plastic on the inner guards.

Just my 2 cents worth

i had the swaybar on and still had some problems with this. after a few 25 ft long jumps, they started to peel off so i just yanked em out. no more problems. now i have the sway bar and still no worries on rubbing. you can always just let it rub, or just take em out. BUT i do suggest taking the swaybar off.... really improves the ride/handling/flexing of the front end.

[murcod]

Out of interest I checked the revs VS speed last night...

100km/h = 3450 RPM (not overly high in my books for a four cylinder)

110km/h = 3800 RPM

[murcod]

BTW that gives a theoretical top speed of 188km/h @ 6500RPM

[HeathGQ]

BTW that gives a theoretical top speed of 188km/h @ 6500RPM

I got mine to 160 once..... still drove well too...