rhills said:
Sam,
Now that you have been down the big tire large travel route, what are your thoughts about the performace gains of this route (assuming things were strong enough)?
Rich
Having the 42s really has been a huge learning curve. If you want to know whats deficient about your suspension setup, throw on a big set of tyres and let your rig behave really badly.
The gains from using big tyres really can be huge although its much harder to get everything to work with them. When I first put them on I really struggled with getting my rig to behave. On a lot of my old track which were easily driven on 36s, Id have trouble on the 42s which was a real eye opener. I could still drive them and crawl slowely but if i got any wheelspin or a bit offcamber or a bit vertical things would fall apart. The big tyres did allow me to drive much harder stuff but the easy stuff was harder and the impossible stuff was more possible. At that point having the 42s gave me much better clearance, approach and departure angles and the ability to make small rocks and ledges insignificant. This allowed me to try and drive a lot more harder stuff. At this point a was really carefull with the throttle and not driving aggressively bacause if I did things would get out of control and start to bounce and hop. Couldnt drive anything too vertical cause it would fall over backwards (which I thought was just a too much lift with too much tyre on too short a wheelbase but this was proved wrong)
In my rigs current form it really does work well. Its got the bwt18 gearbox which gives a crawl of 85:1 which is really good, stock radius arms in the front with drilled bushes (instead of a hinged arm) which I think works really well and longer upper and lower arms in the back that are parallel so gives really low anti squat (dont know the percentage but i should work it out)
Now that everything is sorted (and it is sorted better now than it ever has been with any tyre size) the big tyres really do work amazingly well. The stuff I was driving before with the 36s is now just nothing but a road and not even worth thinking about. Some of the old hard obstacles that I used to play on and test things on (with the 36s and initially the 42s) I now just come up to them and drive them without any thinking. I would use more throttle now and hit things faster than I ever did before and is probably the reason why im breaking so much more. I can really use a lot more throttle because it doesent bounce or lift front wheels (obviously there are limits). Im a lot more confident on the verticle stuff (short climbs that are longer than my wheelbase) which again means I use more throttle (I also got a racing seat and a 4 point harness which helps as well).
But what I am thinking is that as you get into bigger and bigger obstacles then tyre size doesent really matter as much. If the abstacles are in the 0 to 3 foot range a 42 is going to do much better than a 35 or 37. But as the rocks become boulders and the steps become ledges then the size of the tyres isnt as important IMO as long as you still have the approach and departure angles and clearance. For example if the abstacle is composed of rock that is in the 5 to 10 foot slab range tyre size isnt as important as long as you have enough clearance.
I think same thing goes for wheel travel. Once you start playing in big obstacles 5 to 10 foot and bigger range the whole rig tends to be on the obstacle at once so that wheel travel isnt as important and stability (not falling over sideways and not falling over backwards) becomes more so. Which in my mind means that stiffer captured springs, less travel and low C or G would be really advantageous in a lot of situations. I think you still need adequate wheel travel for the type of stuff that you drive but IMO you really should aim for the least amount of wheel travel that you can get away with as opposed to the most amount wheel travel that you can create.
So given this, on my new rig I really want to try some 37 MTRs on the mog axles, run about a 220lb/in springs all round and the killer mod is that I want to put a vertical air ram on the centre of each axle so that I can control the ride height of the rig and also the vertical spring of the centre of the axle as well (can do this by running pressure on both sides of the piston - havent worked out the numbers but, for example, if there was 100psi on both sides of the air ram it will have a much heigher spring rate then say 10psi). Given that my front axle centre line will be totally in front of the motor this will be easy to do. And given the extra lift needed to run the mogs being able to set the rig up with only 1 or 2 inches of up travel will be necessary in some situations(to give you some idea with only 2in up travel I will be at the same ride height as I am now (and ATM i have about 5in up travel))
Sam
