TheSamba.com :: View topic - rear wiper blade

Mon Apr 25, 2016 10:38 am

Probably a silly topic but thought I'd ask.

My rear wiper blade does not make 100% contact with the window. The wiper is 16" long as I recall, and 4" at the "bottom" of the wiper touches the window and 2 to 3" at the top touch the window, but the middle section is arced away from the glass.

I replaced the wiper blade to see if it was the issue, and it wasn't. So I am guessing maybe the tension spring has elongated over the years to not supply enough "retracting" force to make the wiper lay flat.

I'm guessing my options are:
New wiper arm (Gowesty?)
Bend existing wiper arm
Modify spring (looked at the spring, think modification would be difficult for the benefit)
replace spring (not sure where a replacement exists)

Anyone else have a similar issue and what did you do?

Thanks in advance.

Mon Apr 25, 2016 11:51 am

I am risking being called Captain Obvious.

Wiper blades is one of those things that pay more does not guarantee you get a better product. A lot of hypes, and some blades may not work well for our meek meek Vanagon of gentler design of yesteryears. I used to be very conservative when it comes to blade replacement. I would go to the dealer to buy the replacement inserts. That way I keep the original factory arms. Sometimes they came with the German stainless steel spines, and sometimes didn't. My experience was I get better wiper rubber consistently. Today, I am not sure.

Do avoid the retail blades that has plastic spines. The plastic spines do not slide well in the fingers of the blade holder and can cause what you see. Even with SS splines do check how well they slide on the arm fingers. I have seen smart shade tree mechanic decides the fingers are too sloppy and fixed them by crimped them tight with a pair of noodle nose pliers.

Today, I find the bottom end refills from the brandname generally not too bad. Walmart generally has adequate selections.

Mon Apr 25, 2016 12:15 pm

chase4food wrote: I am risking being called Captain Obvious.

Wiper blades is one of those things that pay more does not guarantee you get a better product. A lot of hypes, and some blades may not work well for our meek meek Vanagon of gentler design of yesteryears. I used to be very conservative when it comes to blade replacement. I would go to the dealer to buy the replacement inserts. That way I keep the original factory arms. Sometimes they came with the German stainless steel spines, and sometimes didn't. My experience was I get better wiper rubber consistently. Today, I am not sure.

Do avoid the retail blades that has plastic spines. The plastic spines do not slide well in the fingers of the blade holder and can cause what you see. Even with SS splines do check how well they slide on the arm fingers. I have seen smart shade tree mechanic decides the fingers are too sloppy and fixed them by crimped them tight with a pair of noodle nose pliers.

Today, I find the bottom end refills from the brandname generally not too bad. Walmart generally has adequate selections.

the most obvious thing to do rather than worry about avoiding retail blades (what ever that means) is to bend the arm or blade holder as needed to achieve better contact between the glass and blade.

I still have the original factory arm on my van and it readily accepts aftermarket blade holders. if I want more tension, I can bend the arm to give more tension.

try bending the arm and or blade holder and see if that helps, if not, it could be bent back to the way it was. Who knows, maybe the arm was bent the wrong way at one time and is no longer correctly bent.

good luck, good vision to you.

Mon Apr 25, 2016 12:26 pm

I took some measurements using a digital fish scale at the pivot point of the wiper blade and you may find helpful. My 89 is in excellent shape and so are the wipers. I measured the spring force in oz perpendicular to the windshield. I took care to zero out the scale, as well as only lifting it a tiny amount.

2005 Mini Cooper:
front 18" blade = 27 oz
rear 11.5" blade = 18 oz

Vanagon:
front right blade 18" = 25.1 oz
front left blade 18" = 25.6 oz
rear blade 16" = 14.8 oz

you can see the rear arm on the Vanagon has less spring force even taking into account the shorter blades. I think is is normal as it fight less of aerodynamic lift. I should note that the Mini rear wiper is all plastic so is poorer in compliance to the contour of the glass curvature. Probably why it has pretty strong force compared to the Vanagon's rear.

Bending the arm don't necessary give you more spring force , without studying the over-center action of the design.

Mon Apr 25, 2016 12:34 pm

I should add that compared to the much newer Mini's front wipers, the Vanagon's front is very comparable taking into account the difference in blade length. Hence it supports my inference that the spring force is likely not weaken much compared to when it is spanking new 26 years ago.

My experience and observation is import cars tend to have much lower spring force than American counterparts.

Mon Apr 25, 2016 12:36 pm

chase4food wrote: I took some measurements using a digital fish scale at the pivot point of the wiper blade and you may find helpful. My 89 is in excellent shape and so are the wipers. I measured the spring force in oz perpendicular to the windshield. I took care to zero out the scale, as well as only lifting it a tiny amount.

2005 Mini Cooper:
front 18" blade = 27 oz
rear 11.5" blade = 18 oz

Vanagon:
front right blade 18" = 25.1 oz
front left blade 18" = 25.6 oz
rear blade 16" = 14.8 oz

you can see the rear arm on the Vanagon has less spring force even taking into account the shorter blades. I think is is normal as it fight less of aerodynamic lift. I should note that the Mini rear wiper is all plastic so is poorer in compliance to the contour of the glass curvature. Probably why it has pretty strong force compared to the Vanagon's rear.

Bending the arm don't necessary give you more spring force , without studying the over-center action of the design.

No need to study the over center action of the design, simply bend the arm and see if it works or not, if not, then put it back. No need to over think this here or worry about retail blades Maybe the blade or arm has been adulterated and simply needs to be made right by bending.

Mon Apr 25, 2016 12:40 pm

Right! No need to work your brain too hard is definitely a word of wisdom. :shock:

Mon Apr 25, 2016 12:59 pm

chase4food wrote: Right! No need to work your brain too hard is definitely a word of wisdom. :shock:

back to not ignoring me again, good for you, welcome back!

the original poster can simply try bending the arm. It helps to "study" the right thing, study of irrelevent stuff is a waste. Study what happens when the arm is bent rather than study the fish scale tension on a MiniCooper blade. It takes wisdom to determine what is, and what is not useful to "study" to fix the problem.

Mon Apr 25, 2016 1:06 pm

bluebus86 wrote: ...study of irrelevent stuff is a waste.

One often finds what is irrelevant today is important tomorrow.

not learning something because one finds it irrelevant is only doing ones self injustice.

*edit:* more on topic... I think the OP should try bending it, as stated he already bought new blades and that didn't have the desired result. If bending it doesn't work, replace the arm and spring with new digs.

Mon Apr 25, 2016 1:27 pm

I have no idea how much attention the OP paid to the wiper blade designs. Most European auto utilize the traditional blade design similar to that in the illustration here:

I am the first to admit when I first encounter wiper blade problem, it took a bit of careful study to realize how it all work. On this design only one end of the blade is held fixed - the side that has a locking barb (left hand side end). The rest of the blade floats in the remaining five fingers of the metal frame. There are two SS spines (only one shown here) that supports the rubber squeegee blade. It help support the span of the squeegee between the fingers to spread the force evenly. In some cheap blade a plastic stripe is used that eliminates the two SS spines altogether. These are shit blades to avoid.

Even with the typical ones you can buy like in the illustration above, some are worst than others. I always prefer to keep the factory frame unless they are worn or damaged.

While you can bend the arm to gain a bit of spring force, you have to bend it a lot to make a material difference, and it will be very unsightly. The right solution is to get to the bottom true cause(s) of the problem.

Mon Apr 25, 2016 1:54 pm

Even Sir Bentley tells you to bend the arms if you're having contact issues.

For the record, here's my '90's rear wiper arm and it makes 100% blade contact:

Mon Apr 25, 2016 2:05 pm

Mon Apr 25, 2016 2:07 pm

Thanks all for the insight. I am appreciative of the very technical and the more "try this" approach. My concern with bending the wiper arm is not knowing how brittle the material might be.

I didn't even consider to check the Bentley.

Thanks.

Mon Apr 25, 2016 2:17 pm

Sir Bentley is always right, at least when it comes to direction wise. Bending the arm will increase the spring force F = xC where x is displacement, and C is spring constant. What is C is the key.

Risking prematurely wearing out my binary brain, I went and make some measurements. The scale wanting to do peak hold makes it more challenging, but I succeeded.

Lifting the blade just a bit but make sure no point of the blade make contact with the glass = 25 oz

Lifting the blade an inch higher = 26 oz

A whopping 4% increase if you willing to bend that much.

Mon Apr 25, 2016 2:21 pm

dsdunbar wrote: Thanks all for the insight. I am appreciative of the very technical and the more "try this" approach. My concern with bending the wiper arm is not knowing how brittle the material might be.

I didn't even consider to check the Bentley.

Thanks.

the arm is not brittle, probably could bend it into a pretzel.

Mon Apr 25, 2016 2:22 pm

dsdunbar wrote: My concern with bending the wiper arm is not knowing how brittle the material might be.

It's pretty stout. Bend it in small increments; a small bend can make a big difference.

chase4food wrote: What happen to the aerodynamic spoiler on your arm?

It's on the front left wiper arm, where it's always been. :popcorn:

Mon Apr 25, 2016 2:24 pm

DwarfVader wrote: bluebus86 wrote: ...study of irrelevent stuff is a waste.

One often finds what is irrelevant today is important tomorrow.

not learning something because one finds it irrelevant is only doing ones self injustice.

*edit:* more on topic... I think the OP should try bending it, as stated he already bought new blades and that didn't have the desired result. If bending it doesn't work, replace the arm and spring with new digs.

not attempting the obvious fix and instead measuring the spring force on other cars is a waste of time, not all knowlegde is useful, specaily at the expense of learning something that is useful.

Mon Apr 25, 2016 2:24 pm

The posted excerpt from the Bentley is correcting the till (or perpendicularity) of the blade squeegee, not to increase the downward force and mentioned numerous times in this thread. The perpendicularity is very important.

Mon Apr 25, 2016 2:28 pm

chase4food wrote: Sir Bentley is always right, at least when it comes to direction wise. Bending the arm will increase the spring force F = xC where x is displacement, and C is spring constant. What is C is the key.

Risking prematurely wearing out my binary brain, I went and make some measurements. The scale wanting to do peak hold makes it more challenging, but I succeeded.

Lifting the blade just a bit but make sure no point of the blade make contact with the glass = 25 oz

Lifting the blade an inch higher = 26 oz

A whopping 4% increase if you willing to bend that much.

14.8 to 25 oz force on the rear blade is not too bad. after all you did at first report 14.8 oz for it.

no study of the over action design was required.

I am glad you came around and tried it rather than study the design. see it pays off to not ignore me.

Mon Apr 25, 2016 2:35 pm

bluebus86 wrote: chase4food wrote: Sir Bentley is always right, at least when it comes to direction wise. Bending the arm will increase the spring force F = xC where x is displacement, and C is spring constant. What is C is the key.

Risking prematurely wearing out my binary brain, I went and make some measurements. The scale wanting to do peak hold makes it more challenging, but I succeeded.

Lifting the blade just a bit but make sure no point of the blade make contact with the glass = 25 oz

Lifting the blade an inch higher = 26 oz

A whopping 4% increase if you willing to bend that much.

14.8 to 25 oz force on the rear blade is not too bad. after all you did at first report 14.8 oz for it.

no study of the over action design was required.

I am glad you came around and tried it rather than study the design. see it pays off to not ignore me.

I only read your posts here because you will try to poke any holes you can find. The last set of measurement is to just to prove a point and I use the front wiper for expedience. The rear wiper is inaccessible unless I open the garage. A good technician know what make and not make a difference when it comes to designing an experiment. Please don't overthink this if your eyes begin to glaze over...

Let me repeat. The baseline vs additional 1" lift force difference is conducted on the right front wiper. It gives only 4% increase in spring force.

I promise to return you back to my ignore list.