Date: Sun, 13 Jun 2021 17:04:02 +0000
Reply-To: Richard Koerner <rjkinpb@SBCGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Richard Koerner <rjkinpb@SBCGLOBAL.NET>
Subject: Re: Fresh start, putting on the brakes!
In-Reply-To: <CY4PR0801MB3731664D6FD57A22529E15CCA0329@CY4PR0801MB3731.namprd08.prod.outlook.com>
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Thanks for the reminder that increasing rubber OD on tires also makes for decreased braking performance. Folks with more powerful engine swaps are sometimes eager to go with larger OD tires to improve MPG and freeway cruising speed at lower RPM, but forget this important point.
On Sunday, June 13, 2021, 7:12:43 AM PDT, Dennis Haynes <d23haynes57@hotmail.com> wrote:
There are many considerations for using and maintaining the brake system and yes, there is room for improvement. Different drivers also look for different expectations and since most of us drive other vehicles there is the "similarity" factor each time we get behind the wheel.
To begin with, owning and driving a Vanagon there are simply some design differences especially as compared to most modern vehicles. Most every system is lacking in some way and yet there are few design features that were way ahead for there time. My son has a 1982 Dodge B150 Cargo Van, slant 6, 4 speed on floor, no power brakes or steering. He picked it up a few years ago, used on a farm, has less than 40K on it. It leaks, due to carburetor design, it smells, gets about the same fuel economy as a Syncro, and like a Vanagon needs to be downshifted to get anything that may be a hill. The tires and brakes are huge compared to the Vanagon but the pedal effort for the brakes and clutch is likened to an exercise machine and you really don't want to have to parallel park it. It much as it is stout, the Vanagon is a much better ride!
So while suppliers of brake upgrade kits may tout how unsafe the Vanagon brakes are partly to sell their wares you need to consider your real needs. I often fall to the school of bigger or more is better but have learned that sometimes the improvements may be perception only are self justification. For our brakes I think some though to the why the original designs are there can help to a future path. VW designs seem to evolve in very small steps and seemingly when they are forced my market or regulatory considerations.
So for the evolution of the Vanagon brakes we really need to all the way back to 1971. The was the first year for the front discs, brake booster, and almost laughable the change to the j-bead safety wheel, (The beetle and type 3 had the wheel change in 1968). Why wasn't the wheel or even brake change done in 1968 with the body change, front ball joints, and rear independent suspension? The angle/velocity proportioning valve was also added for the rears. !972 saw the upgrade to the Type 4 motor 1.7L with dual carbs. 1973 saw the motor upgrade to 1.8L with EGR, new exterior lights, and the front disc pads increased thickness so that maybe they could go more then 3 oil changes. With little change such as self-adjusting rears that braking system made it to the Vanagon through 1985. Some 84's and 85"s even saw power assisted steering.
For 1986 we saw the Syncro, the 2.lL with upgraded engine management, redesigned coolant system with oil temperature control, different front brakes and upgraded rear shoes. The changes for the front consisted of single piston floating calipers with larger shoes, (surface area),and rotor thickness increased from 13 to 15mm. The rotor diameter though was slightly reduced, probably to make room for the caliper. As part of the change was the offering of a different type of tire. Available now was the 205/70-14XL on 6" wide wheels. This setup didn't become common until 1987 and usually with the aluminum wheels.
So, why is some of this worth noting? From an emergency stopping perspective the stock brakes working properly can lock up the original tires, front and rear. Often rear wheel lock up even on dry pavement was limiting factor. Some magazine testing demonstrated this. As such the real limitation to "stopping ability" is the tires, not necessarily the brakes. As for heat dissipation at the point the tires are slipping much of the energy is being disspated where the rubber tries to meet the road. After the van is topped getting it up to speed again takes so long the brakes have time to cool. I don't know the "numbers" the change to the 205 width tires with the traction improvements not common LT tires helped to reduce the stopping distance with the improved (slightly) brakes.
Another consideration is that for all the years the Vanagon was sold in the US we had the 55 mph National Speed Limit,(NSL). Increased speeds, adding more power, downhill runs, and larger tires all adversely effect the ability of the brakes to do their job. Added to that is the lack of correct parts being used for service along with bad service methods especially for the rears. Many aftermarket shoes for the front do not have the friction characteristics needed and proper rear shoes have not been available from the dealer for years. The correct shoes had 6mm thick metallic linings riveted in place. Common shoes available now are 4mm, bonded, often not curved properly and they don't fill the drum reducing the contact patch to the drum. As both the adjuster and cylinder are on top, unless the shoes are shimmed and fitted at the bottom only a mall patch near the top of the shoes contact the drum to make friction.
As for the fronts doing 80% of the work I doubt that. Maybe yes in front heavy vehicles during panic stops. Larger and heavier vehicles often have much more breaking in the rear. During aggressive stopping it is usually preferred for the fronts to loose grip before the rears. Todd posted this last week. https://www.brakes-shop.com/brakepedia/general/brake-bias-and-performance Consider this for all modifications including lifting the rear, shimming one side to fix lean, and using different tire sizes or types front-rear.
So lets look at some of the common modifications. Part of the system design is pedal effort and response. Compared to many other vehicles the pedal effort appears high, also for some there is significant travel, especially if the rears are out of adjustment or the system has some air entrained in the fluid. The BMW brake booster can help with that perception and yes it can be used with otherwise stock brakes. A larger master cylinder could also be used. The downside here is what can happen during panic braking. As we don't have any form of antilock part of the system design is to reduce lock up. As panic sets a amazing amount of force can be applied to the as adrenaline kicks in. Once you lock them up and then lift your foot braking time is lost. These events are often when that weak brake line or hose presents itself or that worn out clevis at the pedal finally snaps. From the start again our brakes are really limited by the tires.
So, lets look at some brake upgrades. There are a number of kits available for both front and rear and of course many can develop their own solutions. The first common one was the South African kit. This kit required at least a 15 inch wheel. The increase in diameter with larger pads increased the friction available. The vented rotors added to the thermal cooling which again is of no benefit for those emergency stops. The improvement was incremental. For a number of reason though this set up was problematic as warped and glazed rotors were common. This sometimes happens with some other VW rotor based kits. Part of the problem is not upping the rears to match. There are kits that use dual cylinder calipers and some that add vented disc to the rear. These offer that GM car like fast response and no pressure need to hit the brakes some want, especially if teamed up with a larger booster and master cylinder.
Oh, another thought, as engine vacuum has an effect on the brake booster performance, many vehicles use an electric vacuum pump to augment the booster and to also have the booster work after an engine stall.
For me, I look at ease and consistency of install and will it come back. So far the GoWesty kit has not any comeback and the rear discs seem to make for a balanced set up. I think the custom high mass rotors make the difference. Thermal reserve and stability. This past winter I used my 91 auto in snow and was surprised that could actually use the brakes without have the front or rear instantly lock and slide. Yes I had 4 winter tires. The only negative with this kit is that the choice of pads, it takes a really long time for the brakes to get seated and make the improvement solid.
For brake fade on those long downhill runs the real weak link is likely the rear drums. As they heat they will expand calling for more pedal travel. GoWesty does offer a heavy duty finned rear drum. Again, no difference in braking performance except heat dissipation. This drum will fit with 14 inch wheels. As the center is thicker I like to replace the studs with the 56mm even with steel wheels.
I know this is long winded and so much is left out. Maybe I can do better with specific questions. Main points are as follows:
1. Before jumping at upgrades make sure what you have is working as it should.
2. Try different pads and even shoes.
3. If you want it to stop better the first step is the tires.
4. Get the wheel positions weighed especially if you lifted or leveled the suspension.
Dennis
