Are constant tension hose clamps effective?

Our tests show that JCS’s Hi-Torque hose clamps outperform industry-standard constant tension hose clamps.

Please visit our website for more information on this topic.

We are sometimes asked by clients how our hose clamps compare with constant tension hose clamps – a different design of hose clamp to the hi-grip and hi-torque worm drive clamps we manufacture at JCS.

Design flaw

The idea behind constant tension clamps is that during tightening, the Belleville washers compress and act like a spring. When the rubber relaxes, the spring action pulls the band through the housing, making the clamp smaller to compensate for shrinkage in the rubber hose.

However, we believe the basic engineering principles underpinning this design are flawed.

The idea that a spring can modulate the amount of pressure a clamp exerts over time and under a range of extreme environmental conditions just doesn’t hold water – in some cases literally! In effect you are putting a spring in a pressure system, and when the pressure of the fluid exceeds the spring tension you have a leak.

There is no substitute

In our extensive experience, there is no substitute for clamps that are made to the highest quality and strength, combined with innovations such as JCS’s ‘straight line’ housing – which ensures that every thread of the screw is fully engaged with the band to provide more torque.

With competitive price and timely delivery, YOUDE sincerely hope to be your supplier and partner.

We are constantly running tests at our workshop and we recently carried out a number of laboratory assessments on a sample of industry-leading constant tension hose clamps as well as our own clamps to compare how the different designs perform…

Tests prove conclusive

We tested six constant tension hose clamps of different sizes made by a respected clamp manufacturer from the USA. These manufacturers claim that Belleville washers enable the clamps to cope with ‘fluctuating and extreme temperature applications and thermal compensation’.

We ran a number of tests recording at intervals the grip of each clamp on a calibrated test rig to measure the clamping force. These included a 24-hour rubber cold flow test, and a test where the assembly was heated to 125°c for five hours. Both types of clamp were then tested on a hydraulic pressure tester after the cold flow and heat cycle.

In addition, our test professional performed a salt spray corrosion-resistance test, where the clamps were bombarded with salt water. While the JCS clamps remained unaffected, we found rust forming on the constant tension screw in under 24 hours.

The tests also revealed what we’d known all along – that the constant tension ability of the clamps is quite limited and the capacity of the springs to compress can be a liability.  On most tests, under identical conditions, our conventional HTM clamp substantially out-performed the Belleville design.

Contact us to discuss your requirements of Constant Tension Hose Clamps. Our experienced sales team can help you identify the options that best suit your needs.

I see ' more expensive' mentioned several times in this thread....
given how important the things these are holding on ... hoses...and how few of them there are on the car.... I would go for the very best design I could find .... to match the quality of the cars themselves......and make for peaceful sleeping at night... the hassle and cost of a single broken radiator fitting.... would pay for all of these for the life of the car... The first step is to make sure the pipe outer surface is very clean and smooth, including the lip around the outside. Second step is putting the hose onto the pipe all the way over the lip, up to the stop if there is one. Final step is putting the clamp right behind the sealing lip as close as you can without being on top of it. The lip is what seals the hose, not the clamp. Therefore, the clamp isn't really important. The only factor I can see is that the worm clamps cut the hose and squeeze it through the slits of the band.

Pick a clamp, follow the above advice, don't over tighten it, you'll be fine. Quote: Originally Posted by shertex I'm sure there's a proper name for these things...but you know the type of hose clamps that you loosen by squeezing with pliers? Do they have any advantage in certain applications over clamps that tighten with a screw drive? The reason I ask the question is that they are the ones used for the hose connections on the W210 duovalve. But they strike me as something of a pain to get on and off in such a tight space....my inclination, if I every replace a duovalve again, is to use screw drive clamps. First off you need the proper tool to remove the "Constant Tension Clamp or Band" aka spring clamp. Pliers are not the best tool for them. There are a few versions of this tool, one that is like a plier, the other is a cable type to allow you reach tight places. They both lock onto the clamp and allow to easy removal and installation.

Second, my understanding from a GM engineer, is the wide use of constant tension clamps is two fold. The ease of installation during production and most importantly, is because of the wide use of plastic cooling parts.

The plastic necks tend to expand and contract ever so slightly during normal engine operations. With a fixed clamping worm drive clamp, the plastic neck cannot expand or contract, and this will lead to stress and fatigue in the plastic.

With the constant tension clamp, it will allow for this expansion and contraction while providing enough clamping force for the hose. Constant tension clamps hardly wear out and can be reused many times, unless damage from the removal process.

The biggest mistake that most people make is to replace these clamps on plastic necks with a worm drive clamp.

I really do think the use of worm drive clamps is the reason we saw many neck failures in the past on our w123s. This is reason I switched over to constant tension bands on the radiator side.

Attached Thumbnails __________________
123.133 California
- GreaseCar Veg System


Last edited by DeliveryValve; 05-13- at 03:57 PM. I grew up with US made Vehicles form the s-s and all had worm gear type Hose Clamps on them somewhere.

I can say that it is not the Clamp that fails. It is the Hose.

As the other member said about torquing the Clamps. Over tightening them shortens the life of the Hose especially or the Rubber is squeezing out of the slots in the Clamp.

But, even that is not an issue if you get under the Hood of your car and check things once in a while.

For myself I would not like to be on the Road with a clamp like the EZ Clamp and have to remove the clamp and change a Hose on the Road. It might be difficult to remove or damaged during removal and re-installation.

If you get a decent quality stainless steel oned the typical worm Gear Hose Clamps are extremely reliable and can be reused over and over and over without loss of reliability. __________________
84 300D, 82 Volvo 244Gl Diesel Just thought I would include these pics of other types of clamps.

The fist pic is a type of clamp that was used on some US Cars. They worked OK but the Nuts and Screws on the ones I have see were not stainless steel and would often rust up to the extent that the screw would snap off.

Single Wire Spring Clamp. Also seen on older US Cars. The work and are quick to install but when it is time to change yout Hose you find that the Clamp has cut like 1/2 way into the Hose.
There is also a double Wire version that while not as agresses in cutting the Hose still does that.

The click type Clamp may be the one that the OP was speaking of. Looks like i is only good for a specific size.

Another Spring type Clamp. Usually seen on Fuel Lines but they make them larter like up to 2.5 inches. They are usually not stainless and I don't like them as the ears occasionally snap off when you try to remove them also not being stainless the ears or other parts of the Clamp can rust through.

That is all of the adjustable ones I have pictures of in My notes. __________________
84 300D, 82 Volvo 244Gl Diesel I scanned the thread quickly but I don't think I saw mention of the "official" name of those type clamps. It is an "Oetiker" clamp. Oetiker - Connecting Technology The ones you see are called ear clamps. Volvos use them a lot. I'm not going to opine on the relative betterness of one type over another, but I thought I'd post anyway for info.

Rgds,
Chris W.
'95 E300D 441K __________________
Objects in closer are mirror than they appear. Quote: Originally Posted by renaissanceman Where'd you get the spring clamp for the upper radiator hose? I'm not a fan of the worm clamps and would like to replace with an alternative. Constant Tension Bands are usually an application specific item and are not easily available. You can get them from a new car dealer, but you have to match them up. I have also seen them on Amazon and on eBay.

I myself have salvaged them from my local wrecking yard by matching them up.

On my w123, the radiator's OD neck measures about 35mm. Which is the same on your w124 603 radiator.

If you are looking to salvage these clamps from a parts yard, the size is stamped on the tab or ears.

I found a 44mm clamp fits the best. I also found 43mm clamps can work, but it is a little tight going on over the hose at the neck lip. Both are odd ball sizes and can be hard to come by. You will see 42mm and 46mm all the time.

I believe the clamps I salvaged are made by Roto Clip, who is a major supplier of clamps to the automotive industry.

Here is a .pdf of their clamp offerings.
https://www.rotorclip.com/cat_pdfs/ctb.pdf __________________
123.133 California
- GreaseCar Veg System


Last edited by DeliveryValve; 05-13- at 04:15 PM.