Flipping the tranny gears for larger tires

[penz]

Im going to be putting some larger tires (4") on my summit so im going to gear down. Now flipping the tranny gears is going to greatly reduce my top end even though im putting on bigger tires because the tires are not that much bigger than stock. Its not a huge difference like on the merv. So im wondering if anyone has messed around with this on the summit yet? Im thinking either get a smaller pinion or larger spurr to gear down, or flip the tranny gears and get a slightly larger pinion to make up for some of the loss in top end. I have a 18 tooth pinion now so I think I will take the 16 tooth out and throw that on and flip the gears and see how it drives when I get my tires later this week. Im basicaly looking to keep the same top speed but gear down for the slightly bigger tres. Also I run 3s lipo.

[Burned Up]

please post pics and status of your build...id like to know how this runs...as im thinkn of buying a mini mut...to run for some bashing...against my merv jeep i have built...but would like to build a mini crawler out of another one looks like it would have some potential

[MacKenzie28]

I recently put bigger tires on my summit 4". I thought about swapping the gears, but I tried the stock gear setup first and it ran fine. It actually was a little bit faster. I'm running the proline Pro-Line Epic 2.2 beadlocks with HPI Racing Yokohama Geolandar. They also weigh a lot more.

[penz]

Yeah the taller tires are going to make it faster, it also will put more strain on the motor/esc. Also the added weight will add more strain too. What batterys are you running? I'm running 3s and its fast enough so I'm gearing down to save the motor. I already did the tranny swap and threw on a 19 tooth pinion to get some speed back, I also got a 23 tooth if its still too slow. If I'm not happy with the 19 or 23 tooth pinion I will flip the tranny gears back and get a 15 tooth pinion to gear down that way.

[MacKenzie28]

What is the purpose of gearing down with bigger tires, is it to slow the truck down. Could you keep it as stock with slightly bigger tires with out doing damage?

[penz]

The reason to gear down with bigger tires is to put less strain on the motor/drivetrain. If you put bigger tires but do not gear down your rig will go faster. How much faster depends on how big your tires are. So the idea is to keep your rig at the same speed or final gear ratio recommended by the manufacturer regardless of tire size. To achieve this you must change gearing when changing tire size. Now when going from the canyon tires to the geolandars your looking at a .200" difference, not too much, will add about 2 or 3 mph and not too stressfull on the esc/drivetrain. But they do weigh a lot more witch will create more heat, and if your running on 3s like I am your already going faster than you need. So gearing down slightly would be the best idea.

I just tried running my summit with the flipped tranny gears and a 19 tooth pinion on 3s with the stock tires and it felt like I was running on 2s with the stock tires. I have a 23 tooth pinion that im going to put on and with the bigger tires im thinking its going to be a good match.

[MacKenzie28]

Penz thanks for clearing that up. I just weighed the the new tires with the rims (Yokohama Geolandar w/ Epic) and the weighed in at 142g (each) . The stock tires and rims are 85g (each). In your opinion do you think that this is to much weight added to this little guy? Let me know that that 23t pinion works?

[penz]

Penz thanks for clearing that up. I just weighed the the new tires with the rims (Yokohama Geolandar w/ Epic) and the weighed in at 142g (each) . The stock tires and rims are 85g (each). In your opinion do you think that this is to much weight added to this little guy? Let me know that that 23t pinion works?

Its hard to say without running. I would say that if your running and not having any thermal shutdown issues your probably fine. In my case I actually want to slow it down a little. I get my tires today so ill throw on that 23 tooth and see how it runs.

[penz]

I got the 23 tooth on and the tires mounted! waiting for the glue to dr then ill go for a test run. Here are some pics.

[penz]

Wow tires are great!! I only got to run 1 battery cycle, and only on the street but so far I am impressed! Cant wait to take it off road. I think the gearing is perfect for me, flipped tranny gears and 23 tooth pinion feels just right, i would say somewhere in the middle of 2s and 3s speed with the stock setup, probably 5mph or so slower. Being that it is geared down even with the larger tires, and the fact I only run 3s this thing has power to spare! Mid throttle wheelies no problem.

[MacKenzie28]

That looks mint. what rims are those? i'm considering on trying your tranny set up. glad to hear that you like your set up.

[penz]

Yeah I like it a lot so far, im going out tomorrow afternoon to go bash off road ill report how it goes. They are hpi scorch wheels, in gunmetal color. They have a 12mm hex so they slap right on.

[jimbo74]

how come your left rear tire is backwards?

[penz]

Haha you noticed that huh... I just threw them on to take the pic, they are not glued yet, I flipped it around first.

[mulepic]

I just weighed the the new tires with the rims (Yokohama Geolandar w/ Epic) and the weighed in at 142g (each) .

That's a heavy wheel, how much does just the tire weigh? Maybe with and without foam? You're talking about this one right: http://www3.towerhobbies.com/cgi-bin...&I=LXEXA3&P=ML

[penz]

I think those beadlocks are a lot heavier than standard wheels. I would say the goelandars weigh close to any other 4" tire. I do not believe the stock tires had foam, and I could feel it in the handling.

[MacKenzie28]

That's a heavy wheel, how much does just the tire weigh? Maybe with and without foam? You're talking about this one right: http://www3.towerhobbies.com/cgi-bin...&I=LXEXA3&P=ML

Yes those are the correct tires. I uploaded pic of them in "different wheels". I'm not sure how much just the tire weighs, everything was already tighten down when I weighed them. They don't seem to be bring down the performance of the truck due to the extra weight (no heat issues). I like to have a variety of tire options so I take the extra hit in weight for the beadlocks, plus I think they add style.

[MacKenzie28]

What gears do you flip (part numbers) thx

[penz]

Search the forums for a post called flipped tranny, it has a really good pic with instruction on how to do.

[penz]

So on Friday I ran my summit on dirt, sticky dirt I should say.. And within 3 min I busted another driveshaft!.. So My guess it the larger/heavier tires are putting more strain on the driveline even though im geared down. So if your running bigger tires look into the cvd's whenever they actually come out... And in the meantime loosen the slipper. And for me Im having better luck with the revo driveshafts as replacements. Busted 3 summit driveshafts so far, 2 of them while running revo driveshafts, so far looks like the revo shafts hold up better.

[MacKenzie28]

I've had my summit since November running with bigger tires and rims and haven't run into any problems yet (knock on wood). I also changed the pinion to a 15t. If and when the shafts do break I will look into the upgrade. Thanks for the update.

[franzD1]

What gears do you flip (part numbers) thx

this is NOT mine truck, just a pic to show a "how to"

[noir 522]

just bumpin this tranny flip thread for the heck of it (dont wanna have to look for it next time I need it)

stock



flipped

[noir 522]

Any of you mathematical wizards can figure out what the gear ratio will be once the flip is done (disregard the spur and pinion gearing)?

[TheMajekalBum]

That info is on the first tranny picture. It's roughly double the ratio of stock, half the speed twice the torque. Glad to see that pic I made is still floating around to help.

[GaryGuy]

to gear down, you can also increase the spur gear, the 55 tooth (7047) will give you a 10% lower gear ratio

[noir 522]

Finally did the tranny flip. Great torque - I was literally climbing up the walls with one front tire. The truck is MUCH louder. Stomping the gas will make it screech like crazy. If my full size 1/10 summit didnt make the same noise in low gear I would be concerned, its really howls. Slow crawling as expected is great, And speed appears to be about halved, maybe a lil less. I was running a 2s lipo and at nearly full speed I estimate it was near 18mph, but with my newly broken front bulkhead it started to wobble just before full speed. But yea the torque will have you climbing the walls with ease. (locked diffs). As a daily basher I would not recommend it - it really is slow and whiny. But for a trail/crawler build it makes a world of difference. It is also very quick, If I had my slipper tighter I could have done a back flip - as it is I can still pull a wheelie.

Pros -
- much more torque with take off (for climbing or wheelies)
- great control with rock crawling.
- with locked diffs it makes the truck feels much more powerfull and nearly unstoppable, with better tires I could climb the world.


Cons -
- much much slower - my eyes could actually follow the truck instead of seeing a red blur.
- unless you plan on running 3s- 4s lipos you bashers will not like the speed at all.
- My sons truck in training mode is faster (im gonna have to use 4s to beat him).
- parts breakage with the extra torque - my main drive shaft broke loose while doing another wall crawl manuever - partially due to the broken bulkhead.







Did I mention that its loud.

[hskb]

Good thread - tagging along.

[noir 522]

I would suggest the tranny flip together with the new 1/16 diff lock inserts placed in the rear