| 80mm front caliper conversion question [message #338121] |
Thu, 25 October 2018 15:15  |
sandy trout
Messages: 51
Registered: October 2018
Location: texas
Karma: 1
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I plan on switching front calipers over to the aftermarket 80mm.
I found the calipers at Autozone, they changed numbers for the right caliper to C531 and the left one is C530, the old numbers show when you bring up the part. Autozone has no description on these but if you go to Napa, they have a left and right and using left as an example, the SEL4674 which has a 3 5/32" piston and another left one CAL4678 has a 2 15/16" piston. Which piston size would be better, I am replacing the the booster with a sensitized booster and a 34mm master cylinder as i intend to change the rear brakes to discs.
Also the brake hoses at Autozone (77320 and 77421 ) show a GVW of 7500 to 8000. Is this safe?
All this is going on a 78 GMC that was apparently one of the last ones out of the factory that left as a shell and was finished by an outside supplier. It has no model number I can find and has kitchen on the right side and a bathroom with separate shower on the left side.
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| Re: 80mm front caliper conversion question [message #338124 is a reply to message #338121] |
Thu, 25 October 2018 19:12  |
Scott Nutter
Messages: 782
Registered: January 2015
Location: Houston/San Diego
Karma: 4
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Hi Sandy,
Sounds like you have a center kitchen royal. That's a good one. Finished off by coachman.
Treat her right! Any vin or tze number? Sometimes on the code sheet on the inside of the glove box lid. Should have a date stamp on it also.
Scott.
Scott Nutter
1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, Dave Lenzi super duty mid axle disc brakes, tankless water heater, everything Lenzi. Alex Ferrera installed MSD Atomic EFI
Houston, Texas
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| Re: 80mm front caliper conversion question [message #338128 is a reply to message #338121] |
Fri, 26 October 2018 07:39 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Sandy(?),
Welcome to the group, family, cult, asylum.
One of the first things I am going to do is to suggest that you fill in a sigfile. Go to <Control Panel/Account Settings> and scroll down. Put in a real name, we like those here because you will meet other owners and they won't know you from a wet fish, but you will already be friends. A bit about the coach should also be included. In your case, this sounds like a '78 side bath Royale (Coachmen). That tells us a lot. Include any significant mods in the case this changes things. A geographic reference is good to because you may already have a close by brand new old friend that can be of some assistance to you. (Then
you have to scroll down to <update>.)
Do not fret about the GVW of brake lines. That reference is for what trucks it goes on. All hydraulic brake lines are tested to the same DOT specifications for approval. As to changing the rear to disk brakes, I suggest that you hold off until Applied (aka JImK) gets the testing he wants to do done. There are lots of people running different arrangements, and some interesting things are turning up. I would also suggest that you get to an International and talk to Dave Lenzi before you roll into any investment for changes.
Finding your way here was a real good thing too. This is a supportive and helping community that you have probably never experienced before (that is part of the reason for the full sigfile). We are all interested to see that you get to enjoy your coach and what it can do for you as much as we know it can and will.
As said, this is a community like few others and the only other that I know is that of the watermen that are my world, for that reason I have taken to welcoming new owners there much as any new owner or vessel is welcomed there. So,
May the Good Lord bless this coach and all those that set forth within her.
Welcome Sandy(?)
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: 80mm front caliper conversion question [message #338165 is a reply to message #338121] |
Sun, 28 October 2018 07:31 |
77Royale
Messages: 461
Registered: June 2014
Location: Mid Michigan
Karma: 6
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Dave is not on this forum, Emails work but he is a super busy guy so it may take a day or so to reply.
http://www.bdub.net/lenzi/
Thats a partial offering, I know he has middle wheel disk conversion kits as well as several other parts.
77 Royale, Rear Dry Bath. 403, 3.55 Final Drive, Lenzi goodies, Patterson carb and dizzy.
Mid Michigan
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| Re: 80mm front caliper conversion question [message #338170 is a reply to message #338121] |
Sun, 28 October 2018 08:27 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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HT 3s in D load range are iffy - the Royale is a heavy coach. I r5un HT3s in E load range, the cost difference isn't great. When you go to a GMCMI rally, weigh your coach. You're borderline on Ds.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] 80mm front caliper conversion question [message #338186 is a reply to message #338170] |
Sun, 28 October 2018 15:32 |
powwerjon
Messages: 849
Registered: March 2013
Karma: -2
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The cost different between a D and E rated tire is not worth skimping. You can see the weight on the name plate, but believe me you running a lot heavier. Our coach is a Buskirk Chassis #5 weights about 12,400# empty. Loaded up with fuel 75 gal., no water until we get out of the freezing areas and all the needed stuff to spend the winter in Tucson the coach is at 14,600# (weighted at a GMCMI Convention) and we tow a car that we use as a trailer so add another 3800# going down the road.
JR Wright
Michigan
Buskirk Stretch
> On Oct 28, 2018, at 9:27 AM, Johnny Bridges via Gmclist wrote:
>
> HT 3s in D load range are iffy - the Royale is a heavy coach. I r5un HT3s in E load range, the cost difference isn't great. When you go to a GMCMI
> rally, weigh your coach. You're borderline on Ds.
>
> --johnny
> --
> Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> "I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
>
>
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| Re: 80mm front caliper conversion question [message #338190 is a reply to message #338162] |
Sun, 28 October 2018 21:27 |
Rick Staples
Messages: 126
Registered: May 2014
Location: Johnstown, Colorado, USA
Karma: -1
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Sandy,
In answer to your original question, get the 80mm (3 5/32") calipers. Use with quality semi-metallic or equivalent pads. You'll have to change out the front brake hoses (AutoZone part numbers have been posted on vario0us sites, don't have' 'em handy right now). This was the first of several upgrades I made to my brakes and one of the most cost-effective. Next I'd suggest a "sensitized" booster from Jim B or JimK, and a reserve vacuum pump. My .02.
HTH
Rick Staples
Rick Staples, '75 Eleganza, Johnstown, CO
"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien
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| Re: 80mm front caliper conversion question [message #338192 is a reply to message #338189] |
Sun, 28 October 2018 22:30 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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sandy trout wrote on Sun, 28 October 2018 18:07Thanks for all the great info.
I looked at Dave Lenzi's web site and he has a lot of interesting upgrades.
Who is the expert on the brake options?
Sandy,
In truth, no body is....
JimK and Tom P have done some engineering lever testing, but the rest is based on peoples impressions and anecdotal reports.
Jim and Tom can show you data that they can improve the stock brake configuration by 0.1G. (That is a big number in retarding/braking.) I have the original brakes, but with floating backplates (if you are/were a dirt biker) here referred to as reaction arms. The difference they make in the rear brake is very impressive.
We do have a simple to do with Dave, if you need or want it and Dave is selling, don't ask questions. That is what you want.
When we first got this coach, the dragging rear tires bothered me and I did a set of analysis of the situation and that told me that there was no easy fix. This bugged me because I did work two years in foundation brakes for a Detroit OE. I am trying to locate that study in the hopes it will be of value for a set of new tests that are expected to be run pretty soon now. I have hope, but it got a little dimmer today when I found that the archive drive for that period (about 10 years ago) is not cooperating.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: 80mm front caliper conversion question [message #338249 is a reply to message #338247] |
Wed, 31 October 2018 17:47 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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sandy trout wrote on Wed, 31 October 2018 16:48I double checked the Cooper tires, they are HT3 M&S with a load range of E. They are as quiet as the Michelins, but with less than half the price and handle very well.
Thanks Rick for the info about the caliper piston size and the pad selection.
Thanks Matt for the brake info, what does the dragging rear tires refer to?
Sandy,
If you have an unmodified coach and do a panic stop on dry pavement, the way rear wheels will probably lock. If you stay on the for any time at all, you will make flat spots on those tires. There are several attacks for this of varying success. I believe the "Reaction Arm" version of floating back plates is the best as then all 4 rear brakes get to work equally.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: 80mm front caliper conversion question [message #338261 is a reply to message #338121] |
Thu, 01 November 2018 07:51 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Well you chose good tires. I ran Michelin LTX for 12 years no incidents no checking mostly climate controlled storage. Then bought Cooper HT3s 2 years ago. Both balanced out well and provide great ride. I rate the HT3 better on dry roads (sidewall seems slightly more supportive in truck wash) and rate the LTX slightly better in M/S and wet. They have similar tread blocks but the outer rows are solid on the HT3 which may contribute to less squirm but slightly poorer water evacuation and M/S grip. Made in USA. Time will tell.
John Lebetski
Woodstock, IL
77 Eleganza II
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