I have a chassis that I may be looking to put a brushed motor in due to budget constraints.

I'm looking to make the motor as efficient as possible. We run 4-cell with an 8 second breakout and 10min mains so top speed really is irrelevant but runtime is important and not dumping until after the 10min mark is critical. I'd love to get closer to 14-15min out of a 4200 pack if possible.

So I guess the questions are...

Would harder brushes and softer springs to lower the resistance and make the motor more efficient or would I be causing problems elsewhere with this? Would I be better with softer brushes and softer springs?

What is a good efficient brushed motor? I know some people were running the 21T spec on our track, and that's what I still run in Legends, but I don't think that's the best choice.

Any thoughts?

Just a thought, but you might want to try something like the Tamiya silver can motors. Not the strongest motor out there by far, but doesnt draw much power either. So runtime shouldnt be an issue with this motor...

I'm looking to make the motor as efficient as possible. We run 4-cell with an 8 second breakout and 10min mains so top speed really is irrelevant but runtime is important and not dumping until after the 10min mark is critical. I'd love to get closer to 14-15min out of a 4200 pack if possible.
Any thoughts?

Probably depends on your track, but every now and then we used to
run extended lap races, on a 130 foot carpet oval, that ended up in
the 9minute area.
BUT this was in the 3800 era! ( several years ago)
At first, I used the same motor I always did, (monster),
with two green springs, and took 3 teeth off the pinion.
Had so much left in the pack, I went to two teeth.
Last laps were consistent with the middle laps, and this was
rolling into the corners, and gently pulling the trigger.
Ended up just driving normal, 2 teeth off, and had no problems
with 9+ minute runs, laptimes not that far off from 4 minute times...
Get your CAR efficient.... and be smooth.. :thumbsup:

I'd probably look into trying some different motors before worrying about brushes and springs.

That being said, to answer your question, hard brushes (high silver content) and hard springs will increase current draw and would not be the direction to go.

Try narrowing the brushes to get the amp draw down. I run a spec class that still requires 1500 mAHr stick packs in a stadium truck on a big outdoor oval. I tune my motors for 3-5A no-load amp draw at 2V. I once went 5 minutes on one of those packs and was still running at the end. (It was a mistake by the race director - these races are supposed to be 4 minutes.)

I run the 1600 nicd packs on the trinity speed specs for legends and get just over 5min before I dump out...just enough to finish the race and only drop about .25 sec at the end.

The pan car chassis rolls much smoother than the legends obviously and we can run any 4-cell pack. I'm looking into the maxamps 4.4's as an alternative to my IB4200's since they are getting a bit picky on me lately.

Never thought of the silver can motors...wonder if I can get the gearing right to put one of those at an 8 second lap and get decent run time out of it. It should fit easy enough in the pod of an L4O and may be worth trying.

Regarding narrowing the brushes, I would imagine that this would be at the tip only since it needs full contact with the hood to get current.

I'm still going to run my mamba full time, but I just want to get my 2nd chassis as close as I can so that I can lend it out or have a hot spare if needed.

Thanks for the tips so far guys, keep 'em coming :)

Very light springs are the ticket for enduro racing along with hard brushes. We used to run extended races with 5-6 battery changes per race and light springs was the single most important factor in winning those races. Everyone elses brushes came out little nubs; ours showed only slight wear. Use low timing if adjustable like 5 deg., youll have more runtime than you need. hope this helps.

Regarding narrowing the brushes, I would imagine that this would be at the tip only since it needs full contact with the hood to get current.
Yes, just the tips.