When to regear?

[funindubai]

Darshan, great response and down my ally. A spent a few years supporting fuel development to Jordan Yamaha F1 team and will be happy to discuss these off line. Perhaps over a coffee.

PS: On closed loop one can set different lambda targets from stock to gain hp & torque. I agree with you, I have yet to meet a tuner here that is able to talk the BOSCH language and set these on the original ECU's...

[Paul]

Hi guys

I like the idea of bigger tires, but would like to install them with flat fender flares which would enable you to use a zero or 1" lift.
So the Jeep would be at the same height with bigger wheels....... must be better????? Not sure.

The one big issue about going bigger on tire size is the mass increase. The added mass must have an effect on changing speeds. Both acceleration and braking. It will require more energy to change speeds.

Now try imagine trying to accelerate these big tires while bogged down in thick sand. Not sure it will be good. ... unless you have a Hemi under the hood.

I chose (with Katib's advice) BFG A/T:
33 x 12,5 x 15 = 51 Lb

I assumed the taller sidewall would be heavier, but no.

Other popular 33" sizes in BFG A/T are:
285 x 75 x 16 = 55 Lb
295 x 75 x 16 = 58 Lb
285 x 70 x 17 = 55 Lb

In the 35" size:
315 x 75 x 16 = 64 Lb
315 x 70 x 17 = 62 Lb
35 x 12,5 x 15 =54 Lb

Guys who go to M/T (mud tire) will be way heavier.

Regards
Paul

[funindubai]

Paul

came accross this article
http://www.torquecars.com/forums/f119/w ... bad-21961/
and
http://forums.evolutionm.net/09-ralliar ... eight.html

talks exactly about the topic you raise. The key take away for me is that heavier wheels need suspension improvement to maintain ride quality. With my suspension and gearing upgrade, the feels pretty much back to "normal". the higher centre of gravity does create a bit of an instability at speed.

I am unsure how much more torque is required to drive the extra weight and whether this is sufficiently significant to feel if one drives a fairly powerful engine. I cannot feel the difference on my FJ. As someone said, the " light" feeling returns with reregearing

in the dunes, the higher centre of gravity is an issue, which is why I like your idea on keeping the stock height if possible.

[caprihorse]

Guys,

I went through the articles mentioned in outside forums, but I'm not sure if these comments are valid for our situations and driving experience.

In our case the most important is climbing ability, where if the car is not able to climb, it might hold the whole convoy, eventually the leading car would need to change the route because of a single car. We want to drive high and higher, to conquer the highest dunes.
Any unnecessary increase in the weight, if these are exciting looking mud tyres with attractive heavy rims, mamacita, children or jerrycans with additional petrol, may reduce your horsepower significantly and therefore increase the fuel consumption and reduce the length of the trip you can make. Many times, when we did endurance drives, more then 200 km in the dunes, the heavy cars were refusing to continue as they were out of the petrol and we had to finish earlier as we planned.
On the other hand any increase on the height of centre of gravity may cause fatal accidents, as we are driving sometimes horizontally on the walls with the angle up to 70 degrees (I think so and it looks very scary).
Regarding the suspension, shocks and coils or leafs, it is important to have such, that the car can copy the terrain, not to loose the traction. Once the car is jumping, when climbing, the performance is over, even if you would have engine with XX litres and extreme horsepower.
I hope that when you are talking here about re-gearing, you have on your mind to improve the climbing ability, and not to have high speed in flat areas.
At last drive I had the opportunity to drive for the first time Suzuki Vitara, with stock suspension, stock gears, 225/70R16, 1.6L, 4 cylinders, 77HP, on the almost advanced track. This car performed in some situations much better than other modified cars, because of light weight and flag pole as only modification.

[Paul]

Hi CaCapri

I agree with you 100%

Most stock 4x4's are extremely capable, right off the showroom floor. "Mini Me" is a great example of this.

Doing modifications that decrease performance in the sand would be just plain silly, as you mentioned. This would include climbing ability, fuel consumption, drivability, durability, reliability, handling and resistance to roll overs and pop-outs.

Also, doing modification to look cool on Beach road on a Thursday night....is not for true off-road guys.

We are lucky, we really only have sand to drive on, so our setup is optimised for sand and highway use only.

This can also be confusing, when you read books, magazines and the Internet, their setup is always a compromise for rocks, mud, snow, sand and highways. Sometimes their rigs are trailered to events and never see the highway. What is good for a Jeep rock crawling in Moab is pretty useless for us in Liwa.

Any deviation from stock needs to be done very carefully. Even a simple tire selection can change your drive. There was a long thread about tires on an FJ. Some tires are much better than others. Their grip for climbing, their resistance to pop outs, their durability, etc, etc. The best choice was not the stock tire. So when you need tires, considering the testing others have done for you, would it be wise to stay stock?

regards
Paul

[funindubai]

I agree 100% with the contents of the last 2 threads - except for the 70% incline :). If my vehicle were 100% used for the sand the ideal set up would be different to the set up off the show room floor. Suspension upgrades (and quite a few of us in the club have made them) are done primarily with the purpose of improving traction and to improve the capability of loading more steel on the car - heavier bumpers, winches, roof racks, etc. The lift is usually for clearance and I agree that the balance between a higher COG and ground clearance is a fine line. Certainly 6 inch lift kits are not fit for purpose in this region.
Tyre selection as Paul has pointed out is equally important. And frankly speaking I am worried whether the BFG KO's are a good choice for the desert as opposed to a smoother less aggressive pattern...views?
On regearing - agree with capri climbing ability should be improved...if one takes this step

[Wasif Ahmed]

Those BFG's are pretty good for the desert driving. I run mine at 8 PSI and get amazing traction and very few stucks and have never had a pop out from a long time.

They last very long too, mine are now on 90,000 + KM

Totally satisfied with them and will definitely recommend them to others except Shafiq !!!

[caprihorse]

P.S : STOP SPENDDING , START DRIVING

:like:

If somebody say "I want, I want", nobody can stop him :038:

[caprihorse]

I agree 100% with the contents of the last 2 threads - except for the 70% incline :). If my vehicle were 100% used for the sand the ideal set up would be different to the set up off the show room floor. Suspension upgrades (and quite a few of us in the club have made them) are done primarily with the purpose of improving traction and to improve the capability of loading more steel on the car - heavier bumpers, winches, roof racks, etc. The lift is usually for clearance and I agree that the balance between a higher COG and ground clearance is a fine line. Certainly 6 inch lift kits are not fit for purpose in this region.
Tyre selection as Paul has pointed out is equally important. And frankly speaking I am worried whether the BFG KO's are a good choice for the desert as opposed to a smoother less aggressive pattern...views?
On regearing - agree with capri climbing ability should be improved...if one takes this step

Look at the pic and say still - "I don't believe it..."