How fast are 1/10 4wd race buggies?
 

I was just using BrianG's speed calculator for my Academy SB V2 Pro. I knew the car was fast (3S lipo,MM 5700KV) but according to the calculator it's doing 73mph geared as slow as I can go. Top end geared up is over 110mph. Not that I think I would ever try to get past 100...

So now my thinking is that I need a smaller KV motor. I'd like to KV to the area of MPH I want, as opposed to RPM of the motor by the voltage I run.

Question is, how fast (mph) do 1/10 4wd electric buggies get on the longer straights they run? I'm talking INFMAR, ROAR type stuff.

Did you enter everything into the calculator correctly? (voltage drop?). That setup is probably better for about 60-70 mph or so, but thats flat out, straight line, pavement running. Also remember that the calculator doesn't take wind resistance ino account, which really does come into play bigtime. And as far as racing setups it would depend on the track, but anywhere from 30-40, on the straight, and it would need to be a smooth straightaway, they get tossed arond more then the 1/8 scale buggies. A guy at the track I race at runs 3S and either the 5700 or the 6900 in his T4, it runs great, so I wouldn't worry too much. If you do want a lower kv motor the 4600 would probably be a better choice, or traxxas's 3500. But it's great to do a speed run every once and a while, especially when new people to R/C are around.

4WD electric are going to be your fastest 10th scale offroad class. I would say they would be right at 40 with a race setup (2s pack).

IMO, 30 is more then enough...

But why not go down to the track and see what there running?

The 4wd mod class at my track uses 6 cell nimh for racing and I'd say they're in the mid 30's mph.

I too would say mid 30s. On Sunday I raced my CRT.5 which is good for ~40mph (3s Lipo on Feigao 9L and truck Holeshots) in the 1/10 4wd mod buggy class, and down the straight I literally overtook a buggy (accidentally ran over it).

Accidentally aye MetalMan??? ;)

Ok, 30-40 MPH depending on the track. The LHS is 2.5 hours away so this car does see plenty of street time. The speed calculations were with the 2.5" diameter street tires. The 100mph+ was on the 3.5" stock tires. The track is very small and the front straight is only 30 feet or so.

I used 3.7 volts per cell for the calculations, should I have gone much lower? I cranked up the lipo saver to 3.5v per cell and didn't see any performance drop on a reasonably fresh pack.

The buggy is just over 3.5lbs, has a 2.3:1 diff ratio and I run 16-26 tooth pinions with the 78-80 tooth spur gears. I'm going to put ZX5 pinion gears in the diffs that will up the ratio to 2.83:1 and slow it down a bit.

Not sure what the trany ratio is in my XXXT but it's not as fast with the same stuff in it.

Ok, back to the calculator...
If I go with a Great planes ammo motor at 3300KV, 9.6v (cutoff for my 3S pack) the higher diff ratio (2.83:1), 3.5" tires plus .2" ballooning,76-80 tooth spurs with 16-26 pinions. I get a range from 25.9 to 44.4 mph with a motor rpm of 31,680. Which should cover most tracks right?

If I push the voltage up to 3.5v per cell, I get 28.4 to 48.6 mph with a motor rpm of 34,650.

Then if I want to do speed runs I can throw in a 4s pack for 34.6 to 59.2 mph at 3.2v per cell with 42,240 motor rpm. Push if to 3.5v per cell and I get 37.8 to 64.8 mph with a motor rpm of 46,200.

Those numbers sound good. IMO, the 5700 on 3s is more of a speed run type of thing, not for racing.

I am running a 7700 on 2s in mine and i got to say, its impressive. I am running conservative gearing and running 45+on blacktop