Should I go to 285's?

Submitted: Thursday, Feb 28, 2008 at 22:52
ThreadID: 55024 Views:2277 Replies:7 FollowUps:0
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Hi forumites,
The last time I bought tyres for my 105 GXL 'cruiser, I opted for 265x75x16 as the diameter is pretty close to the 275x70x16's fitted as standard. However, I see that many are opting for 285x75's. Width wise, this would be a better fit on the standard 8 inch rims, but I am wondering how the extra diameter (approx. 1 inch) affects performance.

I know the speedo will be out - I'm more concerned about general driveability and the affect on things like cruising, towing up hills, off-road such as sand, rocks etc. Does the car have to work much harder or need more momentum up steep slopes? Or perhaps there is virtually no noticable difference?

Really looking for actual experience and honest opinions before I spend the money. If you have done it, are you happy, or would you advise against?

Thanks in eager anticipation :)
Gerry
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Reply By: Derek from Affordable Batteries & Radiators - Thursday, Feb 28, 2008 at 23:07

Thursday, Feb 28, 2008 at 23:07
You will feel it yes. Especially if you tow a heavy van, would I fit the same size to my cruiser again ? Yes.

A few photo's here.. B/Ville trip.

I have had the BFG's for 75K and run 6 of them by rotating every 5K. They look new but have started to get 'that' crack where the steel belt sits.

Regards

Derek.
AnswerID: 289929

Reply By: Member - Mark E (VIC) - Thursday, Feb 28, 2008 at 23:50

Thursday, Feb 28, 2008 at 23:50
Gerry,

A couple more things to consider....

Why do you want tyres with increased diameter? The only advantage I can see is slightly more ground clearance over rocky/muddy terrain, so if you do a fair bit of travel in the high country or similar, they may be useful, though the loss of 'crawlability', albeit slight, may offset that advantage.

You don't say whether your car is diesel or petrol. If diesel, like mine, I would be reluctant, as the power for towing, uphills is marginal at best. If a petrol the slight loss of power may be tolerated better.

Also, if diesel, this model has the weaker gearbox (R151 ?) and the bigger tyres would stress this more. Again the petrol has the heavier box and would handle it better (H151 ?)

If I had a turbo diesel or petrol model I would be tempted, but not with the 1Hzzzzz motor. It needs all the help it can get....

Cheers,

Mark
AnswerID: 289939

Reply By: Andrew from Vivid Adventures - Friday, Feb 29, 2008 at 07:45

Friday, Feb 29, 2008 at 07:45
I have done it and am a repeat offender. That would be 180k's in a 1HZ naturally aspirated.

The additional clearance is of value to me - every inch helps, and it is the only inch that lifts your axles and diffs.

That said, I am rarely in a hurry to get somewhere, except a good sunset spot, and sometimes a good sunrise spot. It can be a slow drag and arguably I am more cautious about overtaking as I might have been.

It has not stopped me going anywhere, including across all the dunes of the Simpson and Big Red, Victorian High Country, Kimberley, most of central Australia one way or another to name a few. I am willing to let my tyres down a long way.

Cheers
Andrew.
AnswerID: 289968

Reply By: apriti00 - Friday, Feb 29, 2008 at 09:34

Friday, Feb 29, 2008 at 09:34
As another person has mentioned, why do you want to go this way will give a better understanding of your request. A petrol model should be better able to maintain its normal performance whereas a normally aspirated diesel will feel the difference. I guess we all do it for varying reasons and then accept the changes or continue with other modifications to minimise the change. I from personal experience went from the smaller tyre to a 285 and then onto a 305 and having a t/d noticed a big effect with the second upsize. This change was great for touring as my revs at 100k went down to appprox 1950 but the hills became more taxing of the engine and fuel economy. As I still wanted the taller tyres especially for off road situations I ended up regearing so that with the 285's I am geared a bit lower than standard and when I use the 305's I am still also lower than an 285. In general I was happy with the change and I guess it really depends on what you want to achieve.
Cheers Walter
AnswerID: 289994

Reply By: Crackles - Friday, Feb 29, 2008 at 10:55

Friday, Feb 29, 2008 at 10:55
Gaday Gerry. My 1HZ struggles with the 285's on the road at times particually up hills, overtaking & towing trailers. Accelleration getting up to highway speed is not that different and driving around town you'd barely tell.
Offroad the bigger diameter gives a more comfortable ride, and again as you are either in low range or 1st or 2nd high the difference in available power is not noticeable. 4x4 ability is however much improved giving greater ground clearance for clearing rocks and ledges or getting through mud.
Ideally one would run 2 sets of tyres but the 285 is bareable onroad for the benfits off. I certainly wouldn't go bigger without changing diff ratio's.
Cheers Craig............
AnswerID: 290010

Reply By: Member - Robert G (WA) - Friday, Feb 29, 2008 at 13:40

Friday, Feb 29, 2008 at 13:40
Gerry, I am running 285x75x16 on my TD105GXL and would recomend them. A little more clearance which is always good off road. I am about to fit 305x70x16 tyres whci are essentially the same diameter as the 285's but a little wider, so I do not expect there would be any difference in performance.
AnswerID: 290028

Reply By: GerryP - Friday, Feb 29, 2008 at 18:12

Friday, Feb 29, 2008 at 18:12
Thanks for all your replies folks. Just to answer a few queries raised in this post, the vehicle is a 1HZ with aftermarket Denco turbo.

It's not that I want to go larger diameter, it's just that with the standard 8 inch rims, the 265x75 tyres are a tad narrow, which makes them really awkward to bead out bush and also exposes the sidewalls more than the standard 275x70's. There isn't much choice in the 275 range, hence why I am considering going 285 as many others appear to be doing. The width certainly matches a lot better, but I am concerned about the extra diameter and the overall effect on the vehicle - hence my original post.

Thanks again for all the valuable input.
Cheers
Gerry
AnswerID: 290082

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