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380/150 tire and brake clearance

B

beezee

Active Member
Good morning all,
I've searched around a bit without finding exactly what I'm looking for..

I've been hoping to make the 380/150 tires for on our -8. I just got around to installing the brakes and all on the airplane and there isn't acceptable clearance between the caliper and the rubber of the tire. Mine is currently 1/16"
open


I know folks have run these tires before...did the brake disc have to be shimmed away from the wheel to provide clearance here?

any chance someone running the stock tires can measure the clearance between the rubber and the caliper as a data point?

Thanks!
 
I placed a standard AN washer between the disc and the wheel, that provided me enough clearance for the calipers.
 
Thanks Jake,

Any idea what clearance you've gotten with that? I'd hate to find out the hard way on my first landing that I don't have enough ;-)

Do you take the -7 into North Creek?
 
Br Careful

Jpm757 said:
I placed a standard AN washer between the disc and the wheel, that provided me enough clearance for the calipers.
Click to expand...

That brake disc is designed to seat flat against the wheel. If you place washers between, that's going to put stress on the disc around the washers. I would inspect for cracks often.

My suggestion would be to fabricate a spacer the size of the disc contact area.
 
Mel,
Thanks for the feedback, wheels and brakes get inspected every 50 hrs.. After 300 hrs. everything is holding up fine. The 380/150 tires are a real plus operating in and out of unimproved strips. Regarding the OP question, I will measure the clearance next trip to the hangar.
 
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My wheels and discs are completely stock. I don't know exactly how much clearance I have with the 380/150-5 tires, but it isn't close enough to be a concern. For sure the tire has never touched the caliper.

Are there different depth disc bowls?
 
Same problem on my -8. Initially I made 1/8 shims but was aware there might be a stress concentration like Mel stated. I made shims 1/8 thick and feel better. Tire clearance looks good, don?t know however how much it is - clearance is increasing when brake pads are worn.

qjbbTKH.jpg
 
I live on a dirt/grass strip. 410hrs in 5 years with the 380 tires. Used the washers for spacers. No problems. No rubbing of the calipers against the tires.
When I fashioned the pants, I placed a 3/4" small block on top of the tire as a spacer. This makes the pant a little narrow at the most inferior bolt on the brakes, causing some rubbing of the pant on the bolt head. Has not been a problem. May be good to form the pants with a 1/2" spacer on top of the tire.
The runway has a lot of small grass clumps and can get rough. Have never had a problem with the pants or brackets cracking. (to my surprise)
 
I switched from 500-5 to 380-150 tyres on my (now someone else's) RV-8. The aircraft had standard brakes and calipers. I did not need to make any changes to the brake system.

I did have one issue. One of the first 380 tyres installed "got fat" over the first year. The manufacturer/ supply replaces it.
 
tracy said:
Humpty, did you have to modify your wheel pant?
Click to expand...

Different guy, but the answer to this question will depend on how the wheel pant was originally installed. I originally installed my wheel pants using the standard tire, but I installed them a little bit high for extra clearance, knowing I'd be on some grass from time to time. When I installed the 380x150 tires, they just barely cleared, and I did have to open up the bottoms where the tire comes out of the wheel pant. Thankfully no fiberglass or paint work needed in my case.

If you are not landing on grass, I probably would not bother with this mod. I've even found some grass that I didn't like to roll on even with these larger tires, so they don't turn your RV-8 into a bush plane!
 
Similar to Mickey I ran the stock 5” tires for a few years. Switched to the 380x150 tires when I moved the airplane to our grass strip. Trimmed about 1/2” from the bottom of the wheel pants for clearance. Already had plenty of vertical clearance. No issues with the Matco brake calipers.
 
Carlos151 said:
Similar to Mickey I ran the stock 5” tires for a few years. Switched to the 380x150 tires when I moved the airplane to our grass strip. Trimmed about 1/2” from the bottom of the wheel pants for clearance. Already had plenty of vertical clearance. No issues with the Matco brake calipers.
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I did the same, although I had mounted my pants 1/2" higher than standard to begin with. So I did need to make bulges to clear the brake calipers on the original install. I suppose I lost a knot or so in TAS, not that I notice, when I put the 380x150-5.00 tires on.

For anyone interested, Bob K has the plug/mold for those wheel pant bulges, and HP Aircraft LLC can supply them for $45 + shipping. You can email him at [email protected]. His ad appears on the left side of the 'yesterday's news' section of the VAF home page.

Here are a couple of pictures:
wheelpantbulge.jpg

wheelpantbulge2.jpg
 
Brake clearance

Just resurrecting this thread to see if anyone has the answer to the OP question, i.e. how much clearance is necessary between the brake caliper shoe and the tire?

At the moment I have 1/4" without any shimming between the brake disc and the hub. Hopefully that is enough otherwise the wheel bolts will need to be longer also if there is a shim. This is on a 6A and I'm assuming the wheels are the same as the 8.

Thx
Paul
 

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PaulvS said:
Just resurrecting this thread to see if anyone has the answer to the OP question, i.e. how much clearance is necessary between the brake caliper shoe and the tire?
Click to expand...

Paul, before you call it done on dimensions, consider increasing the disk thickness for more energy storage capacity. The increased tire radius makes the brake less effective, and A-models already tend toward hot disks with the stock 117,500 ft-lb brake. The thicker disk bumps the kinetic energy rating to 155,000.

Cleveland makes an overpriced kit (disk, caliper shoe spacer, longer caliper bolts), but you can easily fabricate your own spacer and source the bolts. The disk is a Rapco RA164-09900, minimum wear thickness 0.275".

I swapped when I went to 380's. Initial braking power is less, a function of tire diameter, but better in the latter stage of the rollout due to less fade.
 
Just replaced my first set of 380X150's after 510 hours, althought there was plenty of even tread remaining, I replaced them due to age. I am using the Matco brakes and have just about a 1/4" clearance using one washer between the rotor and the wheel. My -7 has had these since day one, so I can't speak regarding speed loss, however I believe it to be negligable.
 
DanH said:
Paul, before you call it done on dimensions, consider increasing the disk thickness for more energy storage capacity. The increased tire radius makes the brake less effective, and A-models already tend toward hot disks with the stock 117,500 ft-lb brake. The thicker disk bumps the kinetic energy rating to 155,000.

Cleveland makes an overpriced kit (disk, caliper shoe spacer, longer caliper bolts), but you can easily fabricate your own spacer and source the bolts. The disk is a Rapco RA164-09900, minimum wear thickness 0.275".

I swapped when I went to 380's. Initial braking power is less, a function of tire diameter, but better in the latter stage of the rollout due to less fade.
Click to expand...

Thank you Dan for the suggestion and also for the part number. It looks like they are available from ACS.

Jpm757 said:
Just replaced my first set of 380X150's after 510 hours, althought there was plenty of even tread remaining, I replaced them due to age. I am using the Matco brakes and have just about a 1/4" clearance using one washer between the rotor and the wheel. My -7 has had these since day one, so I can't speak regarding speed loss, however I believe it to be negligable.
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Thanks Jake for confirming 1/4" clearance. If there is a small speed loss it will be a fair tradeoff for me, flying from a grass strip.
 
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